Solid State Batteries: Design, Challenges and Market Demands 3031124693, 9783031124693

Citation preview

Advances in Material Research and Technology

Nithyadharseni Palaniyandy K. P. Abhilash B. Nalini   Editors

Solid State Batteries Design, Challenges and Market Demands

Advances in Material Research and Technology Series Editor Shadia Jamil Ikhmayies, Physics Department, Isra University, Amman, Jordan

This Series covers the advances and developments in a wide range of materials such as energy materials, optoelectronic materials, minerals, composites, alloys and compounds, polymers, green materials, semiconductors, polymers, glasses, nanomaterials, magnetic materials, superconducting materials, high temperature materials, environmental materials, Piezoelectric Materials, ceramics, and fibers.

Nithyadharseni Palaniyandy · K. P. Abhilash · B. Nalini Editors

Solid State Batteries Design, Challenges and Market Demands

Editors Nithyadharseni Palaniyandy Institute for the Development of Energy for African Sustainability (IDEAS) College of Science, Engineering, and Technology (CSET) University of South Africa Roodepoort, South Africa

K. P. Abhilash Department of Inorganic Chemistry University of Chemistry and Technology Prague, Czech Republic

B. Nalini Avinashilingam Institute for Home Science and Higher Education for Women Coimbatore, India

ISSN 2662-4761 ISSN 2662-477X (electronic) Advances in Material Research and Technology ISBN 978-3-031-12469-3 ISBN 978-3-031-12470-9 (eBook) https://doi.org/10.1007/978-3-031-12470-9 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

The demand for alternative power sources for perceiving sustainable/clean energy has created an increasing interest and has become more critical owing to the development of applications such as electric vehicles and new types of portable electronic devices, currently emerging in the market. In order to get LIBs ready for large-scale implementation in Heavy Electric Vehicles (HEVs), researchers tend to improvise or troubleshoot several aspects that connect to performance, stability, safety, and feasibility of large-scale production. Emphasize on all aspects of single electrochemical cells such as novel electrolytes, electrodes, methods to improve the energy/power density, development of high-performance conductive additives/current collectors, efficient packaging, and so on are made. In this realm, among the different battery design strategies, all-solid-state assembly is the promising approach towards the safest technology, giving high energy/power density and reduction in running cost of manufacturing in the growing electronic world. One of the major hindrances or barriers in all-solid-state assembly is the non-availability of in-depth literature to cover from its design strategy to the challenges to be addressed in terms of its interfaces and electrodes. Consolidating the scattered literatures available and analyzing the results on all-solid-state lithium batteries will be the most valid approach to drivel this arena forward to the stage of mellowness and thus to naturalization which is the purpose of this book. The book offers a comprehensive analysis of the principle, Physical, Chemical, and Electrochemical backgrounds and novel design strategies and waste management in higher energy solid-state lithium batteries. This addresses different subdivisions of energy devices such as battery science, energy storage, electrochemical device, and nanotechnology in energy. The book also covers the information on synthesis and experimental techniques and characterization of physical, chemical, and electrochemical properties of the electrodes and electrolytes. The major lacking point in most of the available literature and books is the precise descriptions of the electrochemical measurements of conductivity and related parameters in solid electrolytes and their interfaces, which will be one of the major highlights of this book. It reviews the recent progress and trends of the materials (electrodes and electrolytes), additive

v

vi

Preface

manufacturing technology, and so on for the production of solid-state battery with special consideration for its cost and the market needs. The major highlights of the book include but not limited to the areas such as novel design strategies of all-solid-state assemblies, state of the art of novel electrodes and electrolytes for all-solid-state batteries, solid-solid interfaces and related challenges in all-solid-state batteries, and current situation and the features to be improved in all-solid-state batteries. The book also provides insight into the present-day market scenario on (i) the demand and supply, (ii) the technology of all-solid-state lithiumion batteries and their applications in different energy fields, (iii) narrates various technologies involved such as thin-film, 3D printing (additive manufacturing), atomic layer deposition, and (iv) other recent strategies that have been used for the fabrication of all-solid-state lithium-ion batteries. The description of the complete functioning and challenges with the electrochemistry of the electrodes and solid electrolyte interfaces has been included as a major part in this book. The book also supplies valuable insight into potential growth opportunities in this exciting market and cost-effective design tactics in all-solid-state assemblies. The book caters the knowledge quotient of not only the pursuing scientists but also the budding researchers say, graduate students working on batteries, engineers, and technologists who want a compendium that consolidates knowledge from the fundamentals of battery science to commercialization aspects that demands intradisciplinary understanding regarding the interaction of electrochemistry, solid-state materials science and surfaces and interfaces. Roodepoort, South Africa Prague, Czech Republic Coimbatore, India

Nithyadharseni Palaniyandy K. P. Abhilash B. Nalini

Contents

1

2

Basic Aspects of Design and Operation of All-Solid-State Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P. Priyanka, B. Nalini, and P. Nithyadharseni A Glimpse of Battery Parameters and State-of-the-Art Characterization Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Philips Chidubem Tagbo, Onyeka Stanislaus Okwundu, Johnmary Orjiewulu, Cyril Oluchukwu Ugwuoke, Chukwujekwu Augustine Okaro, Sabastine Ezugwu, and Fabian Ifeanyichukwu Ezema

1

31

3

Prospective Anodes for Solid-State Lithium-Ion Battery . . . . . . . . . . Prabhakarn Arunachalam, Govindhasamy Murugadoss, Chelladurai Karuppiah, Abdullah M. Al-Mayouf, and Chun-Chen Yang

65

4

Prospective Cathode Materials for All-Solid-State Batteries . . . . . . . M. S. Ratsoma, K. Makgopa, K. D. Modibane, and K. Raju

83

5

Prospective Electrolytes for Solid-State Battery . . . . . . . . . . . . . . . . . . 127 Sudheer Kumar Yadav, Suman Yadav, K. P. Abhilash, P. Sivaraj, Zdenek Sofer, and Jörg J. Schneider

6

Novel Design Aspects of All-Solid-State Batteries . . . . . . . . . . . . . . . . . 157 P. Robert Ilango, Jeevan Kumar Reddy Modigunta, Abhilash Karuthedath Parameswaran, Zdenek Sofer, G. Murali, and Insik In

7

Interfaces in Solid-State Batteries: Challenges and Design Strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 P. Sivaraj, K. P. Abhilash, P. Nithyadharseni, Seema Agarwal, Sagar A. Joshi, and Zdenek Sofer

vii

viii

Contents

8

Advanced Characterization Techniques to Unveil the Dynamics of Challenging Nano-scale Interfaces in All-Solid-State Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 K. P. Abhilash, P. Sivaraj, Bhupendar Pal, P. Nithyadharseni, B. Nalini, Sudheer Kumar Yadav, Robert Illango, and Zdenek Sofer

9

Recycling of All-Solid-State Lithium-Ion Batteries . . . . . . . . . . . . . . . 245 K. Ajith, P. Christopher Selvin, K. P. Abhilash, Nithyadharseni Palaniyandy, P. Adlin Helen, and G. Somasundharam

10 Future Challenges to Address the Market Demands of All-Solid-State Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275 K. P. Abhilash, P. Nithyadharseni, P. Sivaraj, D. Lakshmi, Seema Agarwal, Bhekie B. Mamba, and Zdenek Sofer

Chapter 1

Basic Aspects of Design and Operation of All-Solid-State Batteries P. Priyanka, B. Nalini, and P. Nithyadharseni

1.1 Introduction Portable electronics, automobile sectors and grid-scale storage systems have revolutionized today’s world and battery technology plays a vital role in bringing out the key aspects of energy storage and supply. Commercially, Lithium-ion Batteries (LIBs) have been considered to be the hopeful solution in meeting the demand for energy storage systems. In the present commercial batteries, the electrolyte used is 1 M LiPF6 in EC-DMC at 27 °C which has got excellent conductivity of 12 mS/cm which is the goal set for solid-state electrolyte if one wants to replace the presentday batteries with all-solid-state batteries [1]. The electrolyte used in LIBs exist as a liquid, either aqueous/non-aqueous. The use of liquid electrolytes in the traditional LIBs with the presence of organic solvents cause issues on safety problems, thermal runaway and risk of leakage of electrolyte which in turn leads to short circuit and failure of the battery [1]. In 2016, 92 Samsung Note 7 cell phones caught fire which resulted in a large product recall [2]. Notebook computers [2, 3], hoverboards [3] and other Li-ion battery-powered gadgets have also been referenced in fire-related accidents. These accidents are more prone due to the dendrite formation in batteries. The interfacial dendrites formed on the anode create the possibility of an internal short circuit, catching fire and even explosion [4]. The highly flammable nature of the liquid electrolyte leads to dangerous or disastrous consequences due to the leakage P. Priyanka · B. Nalini (B) Department of Physics, Avinashilingam Institute for Home Science and Higher Education for Women, Tamil Nadu, Coimbatore 641043, India e-mail: [email protected]; [email protected] P. Nithyadharseni Institute for the Development of Energy for African Sustainability (IDEAS), College of Science, Engineering, and Technology, University of South Africa, Florida Science Campus, Roodepoort 1709, South Africa e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 N. Palaniyandy et al. (eds.), Solid State Batteries, Advances in Material Research and Technology, https://doi.org/10.1007/978-3-031-12470-9_1

1

2

P. Priyanka et al.

or rupturing in automobile crashes. To alleviate these challenges, All-Solid-State Batteries (ASSBs) comes into play which replaces organic liquid electrolytes with a solid electrolyte. Thermal runaway can be avoided by replacing the flammable liquid electrolytes with a solid electrolyte. ASSBs are not only good at improvising safety but also have a lot of capacity and stability. New-age lithium solid-state batteries are challenging the predominance of traditional liquid electrolyte-based batteries as developments in solid-state batteries reach commercial promise. Solid-state batteries are 80–90% thinner and have a higher decomposition voltage than lithium batteries. As a result, the gravimetric energy density can be increased and the increased energy density will result in higher power output, which will improve all electronic devices significantly [5]. Marching towards the next-generation energy storage technology of electric vehicles (EVs), the global market widely depends on the solid-state batteries with energy density >450 Wh/Kg. Researchers have been working for more than three decades to identify various solid electrolytes in the domains of electrochemistry, material science, polymer chemistry and other fields. Still, the number of feasible solid electrolytes exhibiting high ionic conductivity is inadequate. The incompatibility of these materials with other components of the system, such as electrodes, is one of their intrinsic limits. The close contact between these liquid electrolytes and electrodes is a rate-limiting concern in real systems. Solid electrolytes, when chosen compatible with either electrode, would improve the energy density of the battery. In addition, the advantages of thinner electrolyte and compact packaging can be reaped. Though the use of lithium metal as a negative electrode might double the cell’s energy density, it is desirable to achieve the expected performance with lithium alloys or non-lithium alloys too [6]. The fabrication of all-solid-state batteries includes processing techniques such as printing, pressing, calendaring, etc. Each method has its own set of advantages and disadvantages, which are also described. The need for solid-state battery technology with the identification of good electrode/electrolytes is the major counterpart. Although ASSBs have many advantages over commercial LIBs, their development with commercial viability is limited. Researchers are aiming at this technology for a power-packed future with practicability in the industries which could also satisfy the demand for energy storage, especially in the field of electric vehicles. In this chapter, the different design of battery technology with the processing techniques of SSBs and their interfacial development as full cell is discussed.

1.2 Battery Design A conventional lithium-ion battery comprises of the basic components, anode and cathode immersed in an electrolyte and separated by a separator membrane as shown in Fig. 1.1a. In solid-state batteries, separator and electrolytes are made into one unit since the electrolyte itself would act as both separator and electrolyte. However, in a semi-solid battery where polymer electrolytes are used, the polymer membranes

1 Basic Aspects of Design and Operation of All-Solid-State Batteries

3

Fig. 1.1 a Schematic representation of LIBs [7], b All-solid-state batteries [8] and c Different shapes of batteries [9]

are tailored with conducting salt fillers to achieve the performance of the electrolyte. Hence, every all-solid-state battery would have essentially three components say an anode, a cathode and an electrolyte. Operation of Batteries Solid-state batteries involve a chemistry with redox processes to store and deliver energy. An electrically conductive substance is used to make these two electrodes. An electrolyte containing electrically charged particles is present between these two electrodes. Lithium ions can move through the electrolyte and interact with the anode or cathode (depending on charging or discharging). The transfer of electrical charge between the cathode and anode (through a circuit) is enabled by this chemical process, allowing a battery to generate an electric current to power any gadget. The anode undergoes oxidation, while the cathode undergoes reduction, and the battery can exploit this occurrence to store (charge) and release (discharge) energy

4

P. Priyanka et al.

as needed. In case of an ordinary liquid electrolyte, the saturated ionic salt in solvent offers the mobility of ions, whereas, in the solid electrolyte, ions move through an ion-conductive solid matrix. Figure 1.1b shows the schematic diagram of ASSBs with the major parts and it also shows the challenges faced by ASSBs with metallic anodes (dendritic growth), interfaces (retardation kinetics of SEI formation) and contact issues (loss of contact over electrochemical cycling) [8].

1.2.1 Electrode Materials The electrode materials are the major component of a battery. The role-play of the electrode is to maintain integrity and quality over many charge–discharge cycles. The most commercially used cathode materials are layered oxides such as LiCoO2 (LCO), LiNi1−x−y Cox Mny O2 (NMC), LiNi1−x−y Cox Aly O2 (NCA) & polyanionic compounds such as LiFePO4 (LFP), LiMn2 O4 (LMO), Ni substituted LiMn1.5 Ni0.5 O4 (LNMO) [10–13] and anode materials such as Li metal, graphite, silicon, Li4 Ti5 O12 (LTO), etc., [14] have widely been used in ASSBs.

1.2.2 Electrolyte Materials The solid electrolyte materials can be inorganic or organic type. The disadvantages of organic liquid electrolytes such as severe capacity losses, decreased cycle life, issues with operation temperatures, safety and reliability could be eliminated with the use of solid inorganic electrolyte materials in ASSBs [15]. The main challenge in developing solid electrolyte material is to achieve the highest ionic conductivity at room temperature (10–3 S cm−1 ) and to onset a conducive solid–solid interface of electrode and electrolyte. The solid electrolytes are majorly classified as crystalline and glassy, namely, ● ● ● ● ● ● ● ●

LISICON type, NASICON type, Garnet type, Perovskite type, Glassy type, Ceramic type, Argyrodite type, Solid polymer or polymer composite.

The solid electrolytes with a larger electrochemical window (up to 5 V) are desired for tapping the advantages offered by high-voltage cathode materials as well as of the lithium metal anodes. Argyrodite type of electrolytes with sulphur- and oxide-based compounds such as Li6 PS5x and Li7 Ge3 PS12 offer high ionic conductivity but suffer from chemical kinetics with oxide cathodes and hence it is in the arena of tailoring

1 Basic Aspects of Design and Operation of All-Solid-State Batteries

5

by several researchers. Solid polymer and polymer filler composites are still under trials to reach the high ionic conductivity with fillers of LISICON or Garnet types of electrolytes. Each type of solid electrolyte is advantageous and discussed in the upcoming sections with their processing techniques.

1.2.3 Different Battery Designs The requirement of a battery design depends upon various conditions like how much power is needed or what sort of device portability is required. Different design of batteries have been developed based on the applications employed. Most of the conventional LIBs come in a variety of shapes such as coin cell type, cylindrical, prismatic and pouch type. ● Cylindrical: Cylindrical lithium batteries possess significantly high specific energy and mechanical stability. The design provides additional safety measures and cycles well, has a long calendar life and inexpensive; however, the package density is less than optimal. It’s a popular choice for portable applications. ● Prismatic: For stability, prismatic batteries are enclosed in aluminium or steel. It saves space by being jelly-rolled or layered, but it costs more to make than a cylindrical battery. They’re commonly seen in electric vehicles and energy storage systems. ● Pouch: Lithium battery packed in a compact bag and laminated is a pouch cell. Generally, stacking of individual cells would bring in high internal resistance, however, in a pouch cell, an aggregate of several cells overlaid brings in smaller internal resistance. It is light and inexpensive, but it can be damaged by humidity and extreme temperatures. By preventing delamination, adding a light stack pressure extends the life of the product [9]. The different designs of batteries like all-solid-state batteries, thin-film batteries, thin-film paper batteries, flexible batteries, silicon-based ASSBs, 3D thin-film batteries, single-phase ASSBs and lithium metal batteries along with their salient features are discussed in the below section.

1.2.3.1

All-Solid-State Batteries

The dense lithium lanthanum titanate prepared from spark plasma sintering with lithium manganate cathode and Li metal as all-solid-state battery in the early 2000s, where one of the authors had contributed, yielded 4.3 V at 60 °C [16]. The fabrication of all-solid-state battery using a ceramic type electrolyte, Li|Li5 La3 Ta2 O12 (LLTa)| LiCoO2 , was studied. This ceramic electrolyte LLTa, due to its high Li-ion conductivity and good stability when assembled as full cell, is a prospective candidate for all-solid-state battery. After one complete year of longterm storage, the fabricated cell was found to be operated successfully without any

6

P. Priyanka et al.

deviation of the redox peaks even upon cycling. But the specific capacity obtained was only 4% of the theoretical capacity value and reported that this may be due to low utility of cathode and less wettability of solid electrolyte on LiCoO2 cathode [17]. To overcome these issues, the same group of researchers has worked on threedimensional battery modelling by introducing a three-dimensionally ordered macroporous (3DOM) Li1.5 Al0.5 Ti1.5 (PO4 )3 (LATP) composite electrodes. This is a novel method and provides larger surface area and declines the internal resistance of the cell. The discharge capacity of the full cell containing LATP composite electrodes with a polymer electrolyte shows a discharge capacity of 480 µAhcm−2 and found that the electrochemical performance could be improved by using composite electrodes with higher filling ratios [18].

1.2.3.2

Thin-Film Batteries

All-solid-state battery technology includes thin-film LIBs. Thin-film batteries are lighter in weight, have high energy density and are suitable for wearable devices. Thin-film micro-batteries typically have a Li metal as anode, a polymer type or lithium phosphorus oxynitride Li3+x PO4-x Nx , (LiPON) electrolyte and lithium-based oxides as cathode. LiPON is the most remarkable Solid Electrolyte (SE) developed by Oak Ridge National Laboratory that possesses considerable stability in air compared to other oxide and sulphide-type electrolytes. A thin-film solid-state battery is fabricated using TiO2 anode, lithium––nickel–manganese–cobaltite (LNMC) cathode and LiPON electrolyte and the assembled cell shows a capacity of 52 µAh cm−2 µm−1 (a special unit for thin film batteries) with a capacity retention of 90% over 400 cycles [19].

1.2.3.3

Thin-Film Paper Batteries

Thin-film Li-ion paper batteries have been fabricated using a simple lamination process on a single sheet of paper. This type of flexible battery is rechargeable and exhibits a higher energy density of 108 mWh g−1 . As the total mass of the device is too small with miniaturization these could be employed in RFID tags, wearable devices, functional packaging and new disposable biomedical applications [20].

1.2.3.4

Silicon-Based Thin-Film Batteries

Recently, silicon-based thin-film Li-ion batteries are developed due to the possibility of the formation of intermediate and reversible alloy Li15 Si4 with a theoretical capacity of 3579 mAh g−1 . However, the volume changes up to 300% during lithiation/delithiation process remain a severe drawback with silicon as anode material [21, 22]. Silicon-based anodes are a good choice for ASSBs [21]. But severe volume

1 Basic Aspects of Design and Operation of All-Solid-State Batteries

7

(b)

Fig. 1.2 a Schematic diagram of a thin-film battery. Copyright Permission from [22] ACS Nano., 11(5), 4731–4744, 2017. b Schematic diagram of ASSBs assembled with single-material LGPS Copyright permission from [23] Chem. Commun., 54, 3178–3181, 2018

changes during the cycling process lead to degradation. The introduction of carbon thin-film layer (both on surface and inter layer) upon Si electrode was demonstrated which could increase the electrochemical performance and the mechanical stability (Fig. 1.2a) [22]. The column structure of silicon provides a 1D breathing mechanism like that of lithium which tends to preserve the interface with the electrolyte. The column silicon (col-Si) anode was prepared by Physical Vapour Deposition (PVD) technique and fabricated as a full cell with argyrodite type electrolyte Li6 PS5 Cl and Ni-rich NMC cathode (LiNi0.9 Co0.05 Mn0.05 O2 ,) resulted in an outstanding performance with a capacity retention of 82% over 100 cycles and reversible cycling without shortcircuiting for more than 350 cycles. This report shows an excellent performance with a new kind of column silicon anode with a pouch-type assembly [24]. Slurry mixed sheet type Silicon-Polyacrylonitrile (Si-PAN) anodes along with argyroditetype electrolyte and NMC cathode were assembled in a pellet-type configuration and reported towards the commercialization of ASSBs [25].

8

1.2.3.5

P. Priyanka et al.

3D Thin-Film Batteries

Three-dimensional thin-film batteries has been experimentally realized by Alexander Pearse et al., in 2018 [26]. The 3D batteries show both power and energy density benefits where a pre-lithiated vanadium pentoxide (V2 O5 ) cathode, a very thin layer of Li2 PO2 N solid electrolyte (40–100 nm) and SnNx anode have been employed. The assembling of this battery was done using Atomic Layer Deposition (ALD) technique [26]. Nam et al. [27] explained a process that could improve the ionic conductivity of the electrolyte and demonstrated that the premixing of solid electrolyte and active material would improve the electrochemical performance. The authors have demonstrated the intrusion and the hindrance caused by the polymer binder in the performance and contact. In addition, they have also exploited and reported the effects of both (i) the coating of LiNbO3 on NMC cathode through wet chemical method and (ii) dry mixing and achieved better performance with a scalable process. Lithium nickel cobalt manganese oxide (LiNi0·6 Co0·2 Mn0·2 O2 ) cathode and graphite anode are dry mixed without any addition of binder and slurry mixed with the addition of polymeric binder and assembled as a full system using an argyrodite-type solid electrolyte (Li6 PS5 Cl). The slurry mixed electrodes showed good electrochemical performance and this was taken for full cell fabrication, viz. pelletized cell and an 80 × 60 cm2 (NMC6221 graphite type) pouch-type cell. The pouch-type cell showed a high energy density of 184 Wh kg−1 and analysed for safety tests by charging the cell to 4.3 V at 0.025 C which was then cut with scissors and no noticeable changes were observed and hence justified the mechanical robustness of solid electrolyte [27].

1.2.3.6

Single-Phase ASSBs

In 2015, Han et al. developed a single-material battery made up of Li10 GeP2 S12 (LGPS). As the area of contact, as in liquid electrolyte, could not be achieved, in both transport aspects and infiltrative aspects, with solid electrolyte, high resistance interface and lack of sufficient interfacial contact limit the transport of lithium thus reducing the active sites. So as to address the interfacial problem, a novel singlematerial ASSLIB was developed with LGPS. It acts as a Li2 S cathode and GeS2 anode when LGPS is coupled with carbon that creates active centres of Li–S and Ge–S that are reversible, which in turn reduces the interfacial issues [23]. From the insight of the literature reported in 2012, LiTi2 (PO4 )3 (LTP) solid electrolyte, due to the presence of the Ti4+ /Ti3+ redox pair, more suits to be employed as both electrolyte and an anode [28]. Therefore, in the year 2018, Inoishi et al. thought that if this kind of material could also act as cathode, there is a chance of developing a single-phase ASSBs and found that Cr-doped LTP can satisfy the expectation. The configuration of the assembled single-phase battery was Pt/Li1.5 Cr0.5 Ti1.5 (PO4 )3 /Pt. Hence, this NASICON-type Li1.5 Cr0.5 Ti1.5 (PO4 )3 resulted in superior conductivity and low-interfacial resistance which was beneficial to overcome the interface-related issues [29]. In 2019, Chen

1 Basic Aspects of Design and Operation of All-Solid-State Batteries

9

et al. designed an all-solid-state battery in which the total packaging and components were found to be stretchable. Different stretchable electrodes were reported in literatures but processing them into full cells is described rarely. Hence, assembling a stretchable battery is reported by this team of researchers. The choice of current collector must remain stretchable so as to confirm the elasticity of the cell hence a stretchable carbon composite conductive layer is chosen where Ag nanoflakes were deposited. The stretchable electrodes were fabricated by combining the active materials onto the elastic current collector. This study showed that, on stretching the battery to 50%, a reversible capacity of 28 mAh g−1 and an average energy density of 20 Wh kg−1 were obtained after 50 cycles [29]. Some of the remarkable literatures with the full cell configuration and electrochemical properties are shown in the Table 1.1.

1.2.3.7

All-Solid-State Lithium Metal Batteries

All-solid-state lithium metal batteries are promising candidates since lithium, with its ultrahigh capacity (3860 mAh g−1 ), remains a holy grail for all battery technology and a metal possessing the lowest reduction potential [30]. The Li dendrite growth is prevented by alternate methods of either encapsulating with organic or inorganic compounds. Some of the recently reported remarkable literatures on lithium metal batteries are shown in Table 1.2.

1.3 Processing Techniques for ASSBs The processing of all-solid-state batteries depends on the nature of materials and application to be employed for. There are many techniques which could be employed based on the lab scale or the industrial scale. The processing of full cell using different techniques are discussed below.

1.3.1 Wet Coating Process The wet coating process is a convenient method for large-scale coatings in industries. In this technique, the material to be coated on a substrate is dispersed or dissolved in a liquid solvent. The coated wet film is subjected to drying and post-processing, namely, (i) hot-pressing—that can achieve compaction thus increasing the density or (ii) calendaring or laminating—is also compression of electrodes after drying that reduces porosity thus bringing better contact between the particles, in turn, bringing betterment in energy and power density. Generally, organic solvents used in the preparation of electrodes possess severe environmental and safety concerns which is the necessary point of developing an aqueous process [34]. Due to the fast drying

Li5 La3 Ta2 O12 (LLTa) Amorphous (LiPON)

Argyrodite-type Li6 PS5 Cl

Li-metal

TiO2

Columnar silicon (Col-Si)

Si-PAN

SnNx

LiNi0 .6 CO0 .2 Mn0 .2 O2 /graphite (NCM622)

1

2

3

4

5

6

Gel polymer electrolyte

Li2 PO2 N

Argyrodite

Electrolyte

Anode

S.no.

LiNiCO2

LiV2 O5

Nickel-rich NMC 811 composite

NCM (LiNi0.9 Co0.05 Mn0.05 O2 )

LNMC (LiNi1/3 Mn1/3 CoO2 )

LiCoO2

Cathode

Table 1.1 Design of all-solid-state lithium-ion batteries and their electrochemical performance

Coin cell

Coin cell

Pouch

Thin-film

Pellet

Specific capacity of Pouch type 372 mAh g−1 for 200 cycles at 1C rate and energy density 184 Wh kg−1

Energy density and power density of 3.9 mWh/cm2 and 386 mW/cm2 for 400 cycles at 5 µA/cm2

Specific capacity of 1500 mAh cm−3 at current density 1000 times

Electrochemical performance

[33]

[32]

[31]

Refs.

1 Basic Aspects of Design and Operation of All-Solid-State Batteries 11

12

P. Priyanka et al.

nature that results in fractal formation and discontinuity with aqueous slurries, the demand for organic content in the slurry becomes essential. Aqueous-based electrode preparation methods are hence not suitable [35]. Several techniques such as doctor blade, slot die coating, dip coating, etc. One of the most convenient methods for the formation of composite electrode and solid electrolyte is wet coating technique [36]. Doctor blade technique otherwise known as tape casting or knife coating is the most commonly used technique in batteries [37] and achieves a coating thicknesses 300–500 cycles. Various commercial batteries contain a smaller SiOx (2–10%) in the graphitic anode, providing a modest-capacity gain. Polymer and graphene coatings combined with numerous electrolyte additives will improve Coulombic efficiency and facilitate higher silicon content. Alternatively, limiting the range of silicon lithiation can minimize volume expansion, thereby obtaining a more steady SEI. Graphite-silicon composites present other tasks, comprising mechanical grinding of graphite instigated by silicon expansion/contraction. Calendering graphite to upsurge its actual volumetric energy density will affect more mechanical grinding. Although silicon-based materials will play a

3 Prospective Anodes for Solid-State Lithium-Ion Battery

71

major part in upcoming battery developments, it remains a question of how much battery life and safety outweigh the increased energy density. The answer varies from industry to industry, and silicon is likely to play a greater role in batteries where life and protection are less important.

3.4.1 Carbonaceous Materials and Its Composite as Anode for Solid-State Li-ion Batteries Carbonaceous anode materials also play an effective role in all-solid-state lithium batteries (ASSLBs). At the earliest time, ASSLBs were integrated with different sulfide-based, i.e., SiS2 or P2S2 glass, solid-state electrolytes (SSEs), where the LiCoO2 was used as cathode and graphite as an anode [38]. The study shows the graphite had poor compatibility with SiS2 rather than the P2 S2 glass-based SSEs; because it can be reduced as a side reaction instead of lithium intercalation into the graphite layers during the reduction process, resulting in poor reversibility. Later, Takada et al. [39] constructed a high energy density ASSLBs system with two kinds of SSEs, LiI–Li2 S–P2 S5 glass face to graphite anode and Li3 PO4 –Li2 S–SiS2 glass or Li2 S–GeS2 –P2 S5 face to LiCoO2 cathode. The system indicates that the former electrolyte can stabilize the electrochemical reduction potential and the latter can stabilize the oxidation potential, resulting in excellent volumetric (390 Wh l-1 ) and gravimetric (160 Wh kg-1 ) energy densities, which is more comparable with conventional Li-ion batteries. ASSLBs have further developed with Ni-rich layered (Li2 ZrO3 -coated Li[Ni0.8 Co0.15 Al0.05 ]O2 ) cathode materials in combination with lithium-carbon (LiC) composite as anode and thio-LISICON solid electrolyte (Li2 S-P2 S5 ) [40]. The Li– C composite anode exhibited better electrochemical properties like Li metal, therefore the Li–C|Li2 S-P2 S5 |NCA–LZO based ASSLBs demonstrated an excellent rate capability. In recent years, Tuan et al.[41] had also developed an interface compatible with Li-graphite (Li-C) anode for garnet-type Li6.5 La3 Zr1.5 Ta0.5 O12 (LLZTO) SSEsbased ASSLBs integrated with LiFePO4 cathode. The most effective Li–C/garnet interface was obtained with an interfacial resistance of 11 Ω cm2 while casting Li-C composite paste on garnet SSEs, compared to the pure Li/garnet interface (381 Ω cm2 ). The Li–C|garnet SSEs|LiFePO4 full cell shows comparable cycling performance to the cell with liquid electrolyte, which is credited to the stable Li–C/garnet SSE interface.

3.5 Lithium Metal Anodes for Solid-State Li-Ion Batteries Li metal anode-based Li-ion batteries are mainly called Li metal batteries (LMBs), comprising of metallic Li as anode candidates. It is a potential contender in subsequent-generation batteries such as Li-air (O2 ), Li–S, and Ni-rich cathode-based

72

P. Arunachalam et al.

batteries. Because such LMBs provide greater energy density close to fossil fuel energy density, it is also considered an alternative energy source for global energy demand. In addition, Li metal in classical Li-ion batteries (Ni-rich cathode-based) is mainly used to promote the energy density of the battery system relative to the commercial graphite anode. Since, it has a great theoretical capacity (3860 mAhg-1 ) than the graphite anode. However, safety issues, Lithium scarcity in the environment and short life span tempted by uncontrolled Li dendrite growth are the severe drawbacks in LMBs that limit the Li anode’s practicality. But still, the LMBs play a key part in fulfilling the growing energy demand in the world. Therefore, researchers paid enormous attention to preparing the dendrite-free or stable Li anode by using solid-state electrolytes that include the composite of ceramic fillers with polymer materials and surface modified Li metal strategies which can considerably boost the electrochemical durability and rate features of the solid-state or even liquid-state LMBs.

3.5.1 Solid-State Electrolytes Applying SSEs by replacing liquid electrolytes in the ASSLBs might basically reduce safety concerns. In addition, the electrochemical durability window of SSEs might reach as higher as 5 V and might be applied with high-voltage materials. Likewise, the probability of employing these electrode materials with superior specific capacities is also appealing. SSEs in Li-ion batteries can generally be divided into three groups such as polymeric, inorganic, and composite solid electrolyte (both polymer and inorganic in one) materials. After the invention of the composite solid polymer electrolytes, the ASSLBs have been boosted towards industrialization. Because it can enhance the safety and reduce Li dendrites growth in LIBs related to flammable liquid electrolytes [42]. Owing to the enhanced interface between the CPEs and Li metal anode during Li plating/stripping cycles, the durability and rate capability of ASSLBs show higher performance than the liquid-based LIBs, indicating the great suppression of Li dendrites while using CPEs, which enables the long-term stability.

3.5.2 Artificial Coating Layer or Interlayer Modification for Stable Li Anode Presently, the artificial coating film among Li metal and electrolyte can be classified as integrating ex-situ covering film and in-situ creation of artificial SEIs via electrochemical treatments. To dispel the inherent setbacks of native SEIs, physically decorating functional things on the Li metal surface is anticipated as a practical approach to improve the interfacial durability and reduce dendrite propagation.

3 Prospective Anodes for Solid-State Lithium-Ion Battery

73

Mainly, the classical solution casting approach and innovative emergent approach, comprising chemical and physical vapor deposition, are applied. Organic modified films with greater mechanical deformability and lower density are favorable to steady Li metal anode. For instance, a homogenous polyimide (PI) membrane can be covered over the current collector by employing the doctor blading (DB) method. By adding the mono-dispersed silica nanospheres and reactive-ion etching methods, the PI membrane with vertically nanostructured channels will likely control uniform Li+ flux distribution by hampering horizontal Li+ transport, permitting a smoother, granular Li deposition (Fig. 3.4a). Half cells with an improved stainless steel (SS)-based electrode demonstrated greater collection efficiencies of 97.6% over 240 cycles at 1.0 mA/cm2 . A poly(styrene-co-divinylbenzene) (P(SDVB)) microsphere layer was introduced to shield metal surfaces by these approaches [43]. More importantly, these introduced microspheres might deliver the required mechanical rigidity and govern a homogenous Li-ion distribution. Therefore, the electrochemical durability of the obtained cell was improved by 36% in the Li-NCA (LiNiCoAlO2 ) pouch cell. A higher-polarity β-PVDF polymer film was incorporated into artificial SEIs [44]. This thinner artificial coating layer is described to encourage a homogenous distribution of Li-ion flux and the likely manufacture of favorable SEI components of LiF (Fig. 3.4b). Additionally, these homogenous Li plating at greater current density in the range of 5.0 mA cm−2 and Li plating capacity loadings of nearly 4.0 mAhcm−2 can be attained with the help of β-PVDF films. Further, the active shield of Li metal anode was projected to support the unsatisfactory protection delivered by static SEIs [45]. Also, the modified “solid–liquid” characteristic rising from the covalent bonds between dynamically crosslinked polymers is assessed to contest the dynamic volume variations of Li-anodes, reversibly interchanging among its “liquid” and “solid” things related to the degree of Li growth to deliver homogenously covered surface and dendrite-suppressive influence, correspondingly (Fig. 3.4c). Single-ion-conducting polymers with greatly effective ion transport features are projected to exclude the spacial charge and arrest dendrite propagation. In this regard, Tu et al. demonstrated the structure–property features of lithiated Nafion as artificial SEIs [46]. Adapting a higher-loading NCA electrode of 3 mAhcm−2 , the Li-NCA cells adapted with lithiated Nafion revealed a highly durable process with 3000 mAh g−1 , even at 10 mA cm−2 (17 C)) and discharge capacity upon cycling (2962 mAh g−1 and 2.19 mAh cm−2 after 100 cycles). Compared to thin-film Si anode, Si nanoparticles-based electrodes composed through spray deposition method by a similar group exhibited a high discharge capacity of 2655 mAh g−1 even at a high current density of 5.48 mA cm−2 (24C) [63]. However, the capacity fading in cycling performance of the Si nanoparticlesbased electrode was a bit lower than the Si film-based electrode. It is due to the introduction of nanopores on the Si film electrode that accommodates the volume change, even when the films are thick enough to deliver practical capacities. Hence, it can be concluded that the cycling performance of the nanoparticles-based anode materials can be resolved by optimizing the porous structure. Recently, the ASSLBs were developed using Si nanoparticles/carbon nanofiber (CNF) composite electrode coated with Li6 PS5 Cl SSEs, which exhibits high energy density and excellent cycle stability [62]. The conformal coating of SSEs on the Si/CNF composite surface enhances the interfacial stability between the active material and the SSE, which enhances electrochemical features by suppressing contact loss. Some researchers have focused on Sn-based materials as high-capacity anodes for ASSLBs. Reona Miyazaki and Takehiko Hihara [64] developed Sn nano powderbased ASSLBs with 0Li2S·20P2S5 SSEs, the cell has maintained the capacity of 600 mAh g-1 over 100 cycles. A thick Sn/SSEs composite layer can be spontaneously changed into a dense structure which provides stable cycling and high-rate performance in ASSLBs. Slurry-coated sheet-like Sn-polyacrylonitrile (Sn-PAN) composite anode had also developed for ASSLBs, which displayed the specific capacity of 643.5 mAh g-1 after 100 charge–discharge cycles at a 0.1C rate [65]. The strong adhesion and conformal coating of this mixed (electronic/ionic) conducting

3 Prospective Anodes for Solid-State Lithium-Ion Battery

77

polymer have allowed us to reversibly cycle a slurry-coated electrode without additional inactive conductive additives, resulting in an excellent high-rate capacity of 200 mAh g-1 at 5C. The ASSLBs with SnS nanocrystals and sulfide-based SSEs were demonstrated and exhibited a capacity of 629 mAhg−1 after 100 cycles with a small irreversible capacity in the first cycle (8.2%), while the SnS-based liquid cell showed a rapid capacity decay and large first cycle irreversible capacity (44.6%). The study confirmed that the SSEs prohibited the deprivation of the SnS materials and allowed a reversible conversion reaction, resulting in a highly durable cycling performance [66].

3.7 Transition Metal Oxides as Anode for ASSLBs Transition metal oxides are also considered as high-capacity anode materials in LIBs application. Li4 Ti5 O12 is regarded as one of the most promising anode materials for LIBs, and nanostructured Li4 Ti5 O12 must achieve high electrochemical properties. Spinel Li4 Ti5 O12 possesses a high intercalation/deintercalation potential voltage of 1.55 V vs. Li + /Li, which can effectively avoid the formation of solid electrolyte interphase (SEI) layer and dendritic lithium [67], thus exhibiting high safety [68]. Besides, Li4 Ti5 O12 is a kind of “zero-strain” material with a merely 0.2% volume change during the charge/discharge process [69]. Meanwhile, Li4 Ti5 O12 is low cost and has environmental benignity [70]. The development of ASSLBs with Li4 Ti5 O12 based anode was limited due to the initial consideration of metallic Li anode. However, P.P. Prosini et al. [71] demonstrated ASSLBs based on Li4 Ti5 O12 anode with high voltage LiMn2 O4 cathode and PEO/PEG-based SSEs. The charge transfer resistance of the cell system can be decreased when the temperature increases from 20–40 °C, which evidences that this system can be discharged only at very low currents, restrictive its usage for special purposes, e.g. low-power applications or micro-batteries. More challenges need to resolve for developing the high-capacity metal oxides related anode materials in ASSLBs.

3.8 Summary and Future Scopes Significant features and progress of recent advancements in different anode materials for ASSLIBs have been debated and elucidated in this book chapter. The Li metal anode and electrolyte interfaces are vital channels for Li-ion transport in functioning batteries. Numerous fabrication approaches can enhance the battery performance in Li-ion batteries when adapted with appropriated anode materials. Hereafter, a costeffective, inexpensive synthetic approach is recognized to minimalize the production cost of the anode materials. Further, appropriate aprotic electrolytes that can certify these anodes’ structural durability to employ them in batteries need to be recognized. Although all these studied electrodes for Li-ion batteries, nanostructured composite

78

P. Arunachalam et al.

materials have significantly improved results; however, lower electrochemical durability is considered a major concern when employing these materials. In order to overwhelm these setbacks, two constituents matrices will be adapted in which one matrix performs as a buffer, and others react with Li throughout electrochemical systems. More importantly, surface coating and alterations of the anodes are recommended to evade cracking nanostructures and external oxidation throughout the electrochemical process. The artificial interfacial alteration over Li metal anode is estimated to permit an enhanced ion diffusion as well as distribution, thus attaining dendrite-free structures and a high Li-utilization throughout the cycling process of vital impact for the robust nature of batteries. The protected Li metal anode is projected to tolerate greater current density and electrochemical cycling capacity for commercial usage, whereas uncontainable Li growth features and huge volume transformation are expected. For the research efforts to explore the interfacial engineering between Li and SSE, more consideration must be focused on an emerging approach to renovate “dot-dot” contact into “face-face” contact. We hope that this book chapter will be helpful to understand the challenges and overview of the recent advancements in Li-ion batteries. Also, it helps to provide a vision into favorable outlooks in the energy storage and conversion field.

References 1. Tarascon, J.M., Armand, M.: Issues and challenges facing rechargeable lithium batteries. In Materials for Sustainable Energy: A Collection of Peer-Reviewed Research and Review Articles from Nature Publishing Group, pp. 171–179 (2011) 2. Pacala, S., Socolow, R.: Stabilization wedges: solving the climate problem for the next 50 years with current technologies. Science 305(5686), 968–972 (2004) 3. Zhang, H., Li, C., Eshetu, G.G., Laruelle, S., Grugeon, S., Zaghib, K., Forsyth, M., et al.: From solid-solution electrodes and the rocking-chair concept to today’s batteries. Angew. Chem. 132(2), 542–546 (2020) 4. Dahn, J.R., Zheng, T., Liu, Y., Xue, J.S.: Mechanisms for Lithium insertion in carbonaceous materials. Science 270, 590–593 (1995) 5. Lain, M.J., Brandon, J., Kendrick, E.: Design strategies for high power vs High energy Lithiumion cells. Batteries 5, 64 (2019) 6. Raccichini, R., Amores, M., Hinds, G.: Critical review of the use of reference electrodes in Li-ion batteries: A diagnostic perspective. Batteries 5, 12 (2019) 7. Linden, D., Reddy, T.B.: Handbook of Batteries, 3rd edn. McGraw Hill Professional, New York, NY, USA (2002). ISBN 9780470402528 8. International Energy Agency: Global EV Outlook 2020. OECD, Paris, France (2020) 9. McKerracher, C., Izadi-Najafabadi, A., Soulopoulos, N., Doherty, D., Frith, J.T., Albanese, N., Grant, A., Berryman, I.: Electric Vehicle Outlook 2019. IEA, Paris, France (2019) 10. Logan, E.R., Dahn, J.R.: Electrolyte design for fast-charging Li-ion batteries. Trends Chem. 2, 354–366 (2020) 11. Xu, C., Märker, K., Lee, J., Mahadevegowda, A., Reeves, P.J., Day, S.J., Groh, M.F., Emge, S.P., Ducati, C., Layla Mehdi, B., et al.: Bulk fatigue induced by surface reconstruction in layered Ni-rich cathodes for Li-ion batteries. Nat. Mater. 20, 84–92 (2021)

3 Prospective Anodes for Solid-State Lithium-Ion Battery

79

12. Goriparti, S., Miele, E., De Angelis, F., Di Fabrizio, E., Zaccaria, R.P., Capiglia, C.: Review on recent progress of nanostructured anode materials for Li-ion batteries. J. Power Sources 257, 421–443 (2014) 13. Peled, E.: The electrochemical behavior of alkali and alkaline earth metals in nonaqueous battery systems—the solid electrolyte interphase model. J. Electrochem. Soc. 126, 2047–2051 (1979) 14. Peled, E., Menkin, S.: Review-SEI: Past, present and future. J. Electrochem. Soc. 164, A1703– A1719 (2017) 15. Zhou, Y., Su, M., Yu, X., Zhang, Y., Wang, J.G., Ren, X., Cao, R., Xu, W., Baer, D.R., Du, Y., et al.: Real-time mass spectrometric characterization of the solid–electrolyte interphase of a Lithium-ion battery. Nat. Nanotechnol. 15, 224–230 (2020) 16. Wu, J.J., Bennett, W.R.: Fundamental investigation of Si Anode in Li-Ion Cells. In Proceedings of the 2012 IEEE Energytech, Cleveland, OH, USA, 29–31 May 2012, pp. 1–5. 17. Moretti, A., Sharova, V., Carvalho, D.V., Boulineau, A., Porcher, W., de Meatza, I., Passerini, S.: A comparison of formation methods for graphite//LiFePO4 Cells. Batter. Supercaps 2, 240–247 (2019) 18. An, S.J., Li, J., Du, Z., Daniel, C., Wood, D.L.: Fast formation cycling for lithium ion batteries. J. Power Sources 342, 846–852 (2017) 19. Armand, M., Axmann, P., Bresser, D., Copley, M., Edström, K., Ekberg, C., Guyomard, D., Lestriez, B., Novák, P., Petranikova, M., et al. (2020) Lithium-ion batteries—Current state of the art and anticipated developments. J. Power Sources 479. 20. Wu, Y.P., Rahm, E., Holze, R.: Carbon anode materials for Lithium ion batteries. J. Power Sources 114, 228–236 (2003) 21. Parikh, D., Christensen, T., Hsieh, C.T., Li, J.: Elucidation of separator effect on energy density of Li-ion batteries. J. Electrochem. Soc. 166(14), A3377 (2019) 22. Wood, D.L., III., Wood, M., Li, J., Du, Z., Ruther, R.E., Hays, K.A., Belharouak, I., et al.: Perspectives on the relationship between materials chemistry and roll-to-roll electrode manufacturing for high-energy lithium-ion batteries. Energy Storage Mater. 29, 254–265 (2020) 23. Jaiser, S., Müller, M., Baunach, M., Bauer, W., Scharfer, P., Schabel, W.: Investigation of film solidification and binder migration during drying of Li-Ion battery anodes. J. Power Sources 318, 210–219 (2016) 24. Takami, N., Satoh, A., Hara, M., Ohsaki, T.: Structural and kinetic characterization of lithium intercalation into carbon anodes for secondary lithium batteries. J. Electrochem. Soc. 142(2), 371 (1995) 25. Nordh, T., Jeschull, F., Younesi, R., Koçak, T., Tengstedt, C., Edström, K., Brandell, D.: Different shades of Li4Ti5O12 composites: The impact of the binder on interface layer formation. ChemElectroChem 4(10), 2683–2692 (2017) 26. Wang, Y., Cao, G.: Developments in nanostructured cathode materials for high-performance Lithium-Ion batteries. Adv. Mater. 20(2008), 2251–2269 (2008) 27. Karuppasamy, D., Vikraman, I.-T., Hwang, H.-J., Kim, A., Nichelson, R., Bose, H.S.: Nonaqueous liquid electrolytes based on novel 1-ethyl-3-methylimidazolium bis (nonafluorobutane-1-sulfonyl imidate) ionic liquid for energy storage devices. J. Market. Res. 9, 1251–1260 (2020) 28. Lee, H., Yanilmaz, M., Toprakci, O., Fu, K., Zhang, X.: A review of recent developments in membrane separators for rechargeable lithium-ion batteries. Energy Environ. Sci. 7, 3857–3886 (2014) 29. Xu, B., Qian, D., Wang, Z., Meng, Y.S.: Recent progress in cathode materials research for advanced lithium ion batteries. Mater. Sci. Eng. R. Rep. 73(5–6), 51–65 (2012) 30. Whittingham, M.S.: Lithium batteries and cathode materials. Chem. Rev. 104, 4271–4302 (2004) 31. Kim, H.J., Krishna, T.N.V., Zeb, K., Rajangam, V., Gopi, C.V., Sambasivam, S., Obaidat, I.M., et al.: A comprehensive review of Li-ion battery materials and their recycling techniques. Electronics 9(7), 1161 (2020)

80

P. Arunachalam et al.

32. Balogun, M.S., Luo, Y., Qiu, W., Liu, P., Tong, Y.: A review of carbon materials and their composites with alloy metals for sodium ion battery anodes. Carbon 98, 162–178 (2016) 33. Krauskopf, T., Richter, F.H., Zeier, W.G., Janek, J.: Physicochemical concepts of the lithium metal anode in solid-state batteries. Chem. Rev. 120(15), 7745–7794 (2020) 34. Baggetto, L., Niessen, R.A., Roozeboom, F., Notten, P.H.: High energy density all-solid-state batteries: A challenging concept towards 3D integration. Adv. Func. Mater. 18(7), 1057–1066 (2008) 35. Zhang, W.J.: A review of the electrochemical performance of alloy anodes for lithium-ion batteries. J. Power Sources 196, 13–24 (2011) 36. Cheng, H., Shapter, J.G., Li, Y., Gao, G.: Recent progress of advanced anode materials of lithium-ion batteries. J. Energy Chem. 57, 451–468 (2021) 37. Xin, S., Guo, Y.G., Wan, L.J.: Nanocarbon networks for advanced rechargeable lithium batteries. Acc. Chem. Res. 45(10), 1759–1769 (2012) 38. Takada, K., Nakano, S., Inada, T., Kajiyama, A., Sasaki, H., Kondo, S., Watanabe, M.: Compatibility of lithium ion conductive sulfide glass with carbon-lithium electrode. J. Electrochem. Soc. 150(3), A274 (2003) 39. Takada, K., Inada, T., Kajiyama, A., Sasaki, H., Kondo, S., Watanabe, M., Kanno, R., et al.: Solid-state lithium battery with graphite anode. Solid State Ionics 158(3–4), 269–274 (2003) 40. Ulissi, U., Agostini, M., Ito, S., Aihara, Y., Hassoun, J.: All solid-state battery using layered oxide cathode, lithium-carbon composite anode and thio-LISICON electrolyte. Solid State Ionics 296, 13–17 (2016) 41. Duan, J., Wu, W., Nolan, A.M., Wang, T., Wen, J., Hu, C., Huang, Y., et al.: Lithium–graphite paste: an interface compatible anode for solid-state batteries. Adv. Mater. 31(10), 1807243 (2019) 42. Maleki, H., Deng, G., Kerzhner-Haller, I., Anani, A., Howard, J.N.: Thermal stability studies of binder materials in anodes for Lithium-ion batteries. J. Electrochem. Soc. 147(12), 4470 (2000) 43. Lee, Y.G., Ryu, S., Sugimoto, T., Yu, T., Chang, W.S., Yang, Y., Sun, J.Y., et al.: Dendritefree lithium deposition for lithium metal anodes with interconnected microsphere protection. Chem. Mater. 29(14), 5906–5914 (2017) 44. Luo, J., Fang, C.C., Wu, N.L.: High polarity poly (vinylidene difluoride) thin coating for dendrite-free and high-performance lithium metal anodes. Adv. Energy Mater. 8(2), 1701482 (2018) 45. Liu, K., Pei, A., Lee, H.R., Kong, B., Liu, N., Lin, D., Cui, Y., et al.: Lithium metal anodes with an adaptive “solid-liquid” interfacial protective layer. J. Am. Chem. Soc. 139(13), 4815–4820 (2017) 46. Tu, Z., Choudhury, S., Zachman, M.J., Wei, S., Zhang, K., Kourkoutis, L.F., Archer, L.A.: Designing artificial solid-electrolyte interphases for single-ion and high-efficiency transport in batteries. Joule 1(2), 394–406 (2017) 47. Liu, W., Lin, D., Pei, A., Cui, Y.: Stabilizing lithium metal anodes by uniform Li-ion flux distribution in nanochannel confinement. J. Am. Chem. Soc. 138(47), 15443–15450 (2016) 48. Shen, X., Liu, H., Cheng, X.B., Yan, C., Huang, J.Q.: Beyond lithium ion batteries: Higher energy density battery systems based on lithium metal anodes. Energy Storage Mater. 12, 161–175 (2018) 49. Lang, J., Song, J., Qi, L., Luo, Y., Luo, X., Wu, H.: Uniform lithium deposition induced by polyacrylonitrile submicron fiber array for stable lithium metal anode. ACS Appl. Mater. Interfaces. 9(12), 10360–10365 (2017) 50. Wang, T., Villegas Salvatierra, R., Jalilov, A.S., Tian, J., Tour, J.M.: Ultrafast charging high capacity asphalt–lithium metal batteries. ACS Nano 11(11), 10761–10767 (2017) 51. Cheng, X.B., Peng, H.J., Huang, J.Q., Zhang, R., Zhao, C.Z., Zhang, Q.: Dual-phase lithium metal anode containing a polysulfide-induced solid electrolyte interphase and nanostructured graphene framework for lithium–sulfur batteries. ACS Nano 9(6), 6373–6382 (2015) 52. Zhang, R., Chen, X.R., Chen, X., Cheng, X.B., Zhang, X.Q., Yan, C., Zhang, Q.: Lithiophilic sites in doped graphene guide uniform lithium nucleation for dendrite-free lithium metal anodes. Angew. Chem. 129(27), 7872–7876 (2017)

3 Prospective Anodes for Solid-State Lithium-Ion Battery

81

53. Liu, F., Xu, R., Hu, Z., Ye, S., Zeng, S., Yao, Y., Yu, Y., et al.: Regulating lithium nucleation via CNTs modifying carbon cloth film for stable Li metal anode. Small 15(5), 1803734 (2019) 54. Li, Z., Li, X., Zhou, L., Xiao, Z., Zhou, S., Zhang, X., Zhi, L., et al.: A synergistic strategy for stable lithium metal anodes using 3D fluorine-doped graphene shuttle-implanted porous carbon networks. Nano Energy 49, 179–185 (2018) 55. Sun, Q., Zhai, W., Hou, G., Feng, J., Zhang, L., Si, P., Ci, L., et al.: In situ synthesis of a lithiophilic Ag-nanoparticles-decorated 3D porous carbon framework toward dendrite-free lithium metal anodes. ACS Sustain. Chem. Eng. 6(11), 15219–15227 (2018) 56. Huang, Y., Chen, B., Duan, J., Yang, F., Wang, T., Wang, Z., Huang, Y., et al.: Graphitic carbon nitride (g-C3N4): an interface enabler for solid-state lithium metal batteries. Angew. Chem. 132(9), 3728–3733 (2020) 57. Miyazaki, R.: High-capacity anode materials for all-solid-state lithium batteries. Front. Energy Res. 8, 171 (2020) 58. Tamori, R., Machida, N., Shigematsu, T.: Preparation of Li4. 4Si alloy by use of mechanical milling methods and its properties as negative electrodes in lithium cells. J. Jpn. Soc. Powder Powder Metall. 48(3), 267–273 (2001) 59. Hashimoto, Y., Machida, N., Shigematsu, T.: Preparation of Li4. 4GexSi1−x alloys by mechanical milling process and their properties as anode materials in all-solid-state lithium batteries. Solid State Ion. 175(1–4), 177–180 (2004) 60. Miyazaki, R., Ohta, N., Ohnishi, T., Sakaguchi, I., Takada, K.: An amorphous Si film anode for all-solid-state lithium batteries. J. Power Sources 272, 541–545 (2014) 61. Miyazaki, R., Ohta, N., Ohnishi, T., Takada, K.: Anode properties of silicon-rich amorphous silicon suboxide films in all-solid-state lithium batteries. J. Power Sources 329, 41–49 (2016) 62. Sakabe, J., Ohta, N., Ohnishi, T., Mitsuishi, K., Takada, K.: Porous amorphous silicon film anodes for high-capacity and stable all-solid-state lithium batteries. Commun. Chem. 1(1), 1–9 (2018) 63. Ohta, N., Kimura, S., Sakabe, J., Mitsuishi, K., Ohnishi, T., Takada, K.: Anode properties of Si nanoparticles in all-solid-state Li batteries. ACS Appl. Energy Mater. 2(10), 7005–7008 (2019) 64. Miyazaki, R., Hihara, T.: Charge-discharge performances of Sn powder as a high capacity anode for all-solid-state lithium batteries. J. Power Sources 427, 15–20 (2019) 65. Dunlap, N.A., Kim, J., Oh, K.H., Lee, S.H.: Slurry-coated sheet-style Sn-PAN anodes for all-solid-state li-ion batteries. J. Electrochem. Soc. 166(6), A915 (2019) 66. Kim, S., Choi, J., Bak, S.M., Sang, L., Li, Q., Patra, A., Braun, P.V.: Reversible conversion reactions and small first cycle irreversible capacity loss in metal sulfide-based electrodes enabled by solid electrolytes. Adv. Func. Mater. 29(27), 1901719 (2019) 67. Park, K.S., Benayad, A., Kang, D.J., Doo, S.G.: Nitridation-driven conductive Li4Ti5O12 for lithium ion batteries. J. Am. Chem. Soc. 130(45), 14930–14931 (2008) 68. Wu, L., Leng, X., Liu, Y., Wei, S., Li, C., Wang, G., Zhang, T.Y., et al.: A strategy for synthesis of nanosheets consisting of alternating spinel Li4Ti5O12 and rutile TiO2 lamellas for high-rate anodes of lithium-ion batteries. ACS Appl. Mater. Interfaces. 9(5), 4649–4657 (2017) 69. Daigle, J.C., Asakawa, Y., Beaupré, M., Vieillette, R., Laul, D., Trudeau, M., Zaghib, K.: New avenue for limiting degradation in NanoLi4Ti5O12 for ultrafast-charge Lithium-ion batteries: Hybrid polymer-inorganic particles. Nano Lett. 17(12), 7372–7379 (2017) 70. Wang, J., Dong, S., Zhang, Y., Chen, Z., Jiang, S., Wu, L., Zhang, X.: Metal–organic framework derived titanium-based anode materials for lithium ion batteries. Nano-Struct. & Nano-Objects 15, 48–53 (2018) 71. Prosini, P.P., Mancini, R., Petrucci, L., Contini, V., Villano, P.: Li4Ti5O12 as anode in allsolid-state, plastic, lithium-ion batteries for low-power applications. Solid State Ion. 144(1–2), 185–192 (2001)

Chapter 4

Prospective Cathode Materials for All-Solid-State Batteries M. S. Ratsoma, K. Makgopa, K. D. Modibane, and K. Raju

4.1 Introduction With energy security identified as one of the global challenges of modern society, many efforts have been made to improve the quality of generation and supply so as to meet the requirements and demands of modern day applications. The ongoing (eminent in other parts of the world) transition from the heavy reliance on the ecologically detrimental fossil fuels as sources of energy to the use of renewable resources for the generation of green and clean energy has been adopted to not only improve the energy quality but to also mitigate the adverse environmental effects brought on by the use of fossil fuels since their discovery. However, the intermittent nature of renewable energy resources requires the use of energy storage systems that would ensure a constant and steady supply of energy to applications such as power grid connected to residential, commercial and industrial loads [1–3]. Moreover, the need for state-of-the-art and efficient energy storage systems is identifiable in the quest of meeting the energy demands in applications such as the rapidly changing and growing portable consumer device market and the growing electric vehicle industry [4]. Immense research efforts are been aimed at developing autonomous wireless devices that can be used for smart applications such as smart building control, smart medicine and other ambient technologies. On-board energy storage is essential in such devices in order to maintain and ensure a stable current M. S. Ratsoma · K. Makgopa (B) Department of Chemistry, Faculty of Science, Tshwane University of Technology (Arcadia Campus), Pretoria 0001, South Africa e-mail: [email protected] K. D. Modibane Nanotechnology Research Lab, Department of Chemistry, School of Physical and Mineral Sciences, University of Limpopo (Turfloop), Sovenga 0727, Polokwane, South Africa K. Raju Energy Center, Council for Scientific and Industrial Research (CSIR), Pretoria, South Africa © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 N. Palaniyandy et al. (eds.), Solid State Batteries, Advances in Material Research and Technology, https://doi.org/10.1007/978-3-031-12470-9_4

83

84

M. S. Ratsoma et al.

supply or deliver high peak currents when needed. Rechargeable batteries stand out as the most obvious devices that guarantee energy storage [5]. However, conventional rechargeable batteries involve the use of liquid electrolytes as conducting mediums, as well as separators, which imposes limits on the design and size of batteries. Furthermore, liquid electrolytes carry the inherent risk of leakage and possibly device explosion resulting from the use of flammable organic liquid electrolytes [6]. Amongst rechargeable batteries, lithium-ion batteries (LIBs) in particular have been demonstrated to be capable of meeting the energy storage and supply requirements of modern day applications due to their high energy density compared to supercapacitors and other hybrid systems [7]. The LIB technology is considered as one of the short-term energy storage solutions due to its high energy density and reasonably simple charge storage reaction mechanism. The existing LIB systems are fairly well developed for application in the portable electronic devices, and hence have been dominant and aided the portable electronics revolution for nearly thirty years [8, 9]. However, the need for further LIB component material (electrodes, electrolytes, etc.) and system developments arises as a result of the performance requirements that are raised with regard to the energy and power densities, cycling life, as well as the safety issues for the application of LIBs in large-scale high-power systems that include the plug-in hybrid electric vehicle (PHEV) or plug-in electric vehicle (PEV) [8]. A typical conventional liquid electrolyte-based LIB construct consists of two porous electrodes (anode and cathode) and an electrolyte drenched separator material. The electrodes are usually fabricated by coating the active material onto a current collector, in the presence conductive agents and binder material [10]. The liquid electrolyte, which is generally made from aprotic organic solvents and a conductive salt, facilitates the Li+ ion transfer between the electrodes. However, most of the challenges that plague conventional LIBs can be traced back to this liquid electrolyte; In fact safety concerns in LIBs are an actual consequence of the flammability of the solvents [6]. Besides, side reactions of the solvents and the conductive salt lead to attenuation of the capacity fading and system aging [11]. Moreover, the burdensome electrolyte filling and wetting process, as well as the extensive formation procedure, result in increased production costs during cell fabrication [12, 13]. The adoption of the non-flammable solid electrolytes (SEs) in the form of polymer/gel-polymer and inorganic compounds for LIBs comes as the ultimate solution to overcoming the safety issues inherent with the flammable liquid organic electrolytes. These electrolytes also present the advantage of reaching and surpassing beyond the performance limits that are insight for the climaxing liquid electrolytes systems. All-solid-state lithium-ion batteries (ASSLIBs) exhibit many advantages in comparison to liquid electrolyte-based lithium-ion batteries in the sense of further showing potential for an enhancement of the energy density and life span in addition to improved safety owing to the use of SEs instead of the flammable organic components, they also exhibit [4, 14–18]. Furthermore, the use of solid electrolytes can facilitate the overall miniaturization of the battery pack as seen in Fig. 4.1, which can result in more flexibility for the design of stand-alone microelectronic devices

4 Prospective Cathode Materials for All-Solid-State Batteries

85

and enhance LIB use in applications such as medical implants due to no possible risk of the ever solid electrolyte leaking [5, 18]. All-solid-state lithium batteries (ASSLBs), the available options of electrode materials are vastly expanded due to the wide electrochemical potential window offered by the SEs, giving way to a great potential for developing high potential cathode materials and lithium metal anodes with extremely high theoretical specific capacities [19–21]. However, despite the high conductivities offered by some SEs, a serious challenge in all-solid-state batteries (ASSBs) is encountered with the interfacial contact of solid electrolytes with the electrode active materials. Inherently, the contact area of the SEs and electrodes is highly reduced (contrary to the liquid electrolyte soaked conventional batteries), which results in an inadequate or attenuated conductivity across the interface [22, 23]. In the case of cathodes, high interfacial

Fig. 4.1 Comparison of conventional lithium-ion battery and all-solid-state lithium battery at the cell, stack, and pack levels with potentials for increased energy density [27]. Reproduced with permission from Ref [27]. Copyright Elsevier

86

M. S. Ratsoma et al.

contact impedance is often generated as a result of the poor wetting solid–solid interaction between the cathodes and solid electrolytes. Usually, the interfacial impedance is overcome by interfacial engineering, where inert lithium-ion conductive interfacial buffer layers, which include Al2 O3 , Li2 O-ZrO2 , ZrO2 , LiNbO3 , etc., are introduced either by mixing or adding or by coating onto the surface of either the electrolyte or the electrode so as to enhance the ionic conductivity at the solid–solid interface [24, 25]. This also brings the benefit of circumventing side reactions at the interface, as well as avoiding the formation of interphases (solid electrolyte interphase (SEI)) having charge transport properties that impede the cell performance [26]. As is the electrode–electrolyte contact, electrochemical stability of the electrolyte at cathode potential is also important. Sulphide-based solid electrolytes present an improved contact area due to their ductility [28], but most sulphide electrolytes tend to show high instability towards cathode potentials [29]. Offering protection to the cathode by coating with a polymer layer [30, 31] or an oxide material [32–35] usually resolves the issue. On the other hand, oxide-based electrolytes display improved electrochemical stability against cathode potentials, which is inherent to their very hard particulate nature [30], even exceeding 4 V. Nonetheless, a sintering step may be necessary to enable adequate electrolyte contact with cathode active materials (CAMs) [36], but this can result in undesirable degradation or interphase formation [37]. Hence, stable and effective electrode–electrolyte interfaces with maximized contact areas are necessary to ensure an adequate lifetime and cycling stability in ASSBs [26, 27]. Generally, the magnitude of the cell voltage and the capacity are determined by the CAMs, which are also the limiting factor to the transportation rate of Li+ ions. Thus, the development of CAMs has become greatly crucial and has received considerable attention over the years. Usually, the development and optimization of cathode active materials consider the enhancement of parameters that include energy density, rate capability, cycling performance, safety, and cost. The energy density is usually determined by the CAMs’ reversible capacity and the electrode operating potential. The two latter aspects are themselves reliant on the CAMs’ inherent chemistry, which includes the effective redox couples and optimal lithium concentration in the active materials. The rate capability and the cycling performances are largely determined by the electronic and ionic conductivity capacity of the CAMs, although particle morphologies also play a role as a result of the anisotropic nature of the structures, which in some cases can have an even bigger effect. Hence, materials optimization usually involves a two-headed approach, i.e., changing the active materials’ basic chemistry and modifying the surface and structural morphology (surface architecture, particle size, particle shape, etc.) [8]. Unlike the incredible efforts aimed at improving the ionic conductivity of SEs and overcoming interfacial resistance [38–41], little consideration has been given to the cathode material in the all-solid-state battery system [42]. In that regard, all-solid-state lithium battery technology mostly uses CAMs that are used in the conventional lithium battery technology [43]. The most used cathode active materials in lithium battery technology are the lithium transition metal oxides (Lix M y Oz ) and their derivatives due to their favourable performance properties such as good cycling

4 Prospective Cathode Materials for All-Solid-State Batteries

87

stability and high operating voltage [44]. On the other hand, their relatively low reversible capacity impedes their further development and implementation in the next generation Li-battery technology, which must offer high energy and power densities [45, 46]. This leaves room for transition metal chalcogenides, which generally have much higher theoretical specific capacities than lithium transition metal oxides. Using structure as a classification criterion, conventional CAMs include layered compounds LiMO2 (M = Co, Ni, Mn, etc.), spinel compounds LiM 2 O4 (M = Mn, etc.), and olivine compounds LiMPO4 (M = Fe, Mn, Ni, Co, etc.) [8]. In this chapter, we discuss cathode active materials (CAMs) that can be applied in ASSLIBs, with attention given to the structure, preparation methods, and electrochemical performance. Our discussion covers the lithium transition metal compounds (Lix M y Oz ,), polyanionbased lithium transition metal compounds (Lix M y (XO4 )z ( X = P, S, Si, Mo, W, etc.)), and the nanostructured transition metal compounds (M x X y , X = O, S, Se).

4.2 Basic Principles of Lithium-Ion Batteries (LIBs) 4.2.1 Working Principle of LIBs The basic working principle of LIBs is shown in Fig. 4.2a. The LIBs are generally assembled in a “discharged” state, with all the Li+ ions initially on the cathode side. During charging, the Li+ ions are extracted from the cathode, transported by the solid electrolyte through defects and/or unique double-lattice structures (inorganic SEs) or segmental motion of polymer chains (polymer SEs) [43] (or solvated in and moved through a liquid electrolyte), and ultimately intercalated into the anode host. At the same time, electrons also move from cathode to anode through the current collectors that form the external electric circuit. A greater chemical potential of Li is obtained in the anode than in the cathode, thus energy is stored by converting electric energy to electrochemical energy [8]. The electrode/terminal activity of LIBs can be expressed in the form of chemical equations as shown in Eqs. 4.1 and 4.2, using a LIB built with LiMO2 and graphitelike carbon as the cathode and anode, respectively. During the charging process (forward reaction in Eq. 4.1) the CAM is oxidized, losing x electrons (Li1-x MO2 ), while the anode active material is reduced by receiving x electrons (Lix C6 ) via the forward reaction in Eq. 4.2. The reverse reactions in both Eqs. (4.1 and 4.2) are true for the discharge process. The overall battery reaction is expressed in Eq. 4.3. LiMO2 ⇄ Li1−x MO2 + xLi+ + xe−

(4.1)

xLi+ + xe− + 6C ⇄ Lix C6

(4.2)

LiMO2 + 6C ⇄ Li1−x MO2 + Lix C6

(4.3)

88

M. S. Ratsoma et al.

Fig. 4.2 a Working principle of an ASSLIB during the charging process [8]. Schematic representations of b inorganic solid electrolyte-based and c solid polymer electrolyte-based ASSLIBs [43]. Reproduced with permission from Refs. [8, 43]. Copyright Elsevier and Springer Nature

Images (b) and (c) in Fig. 2 show the schematic representations of inorganic solid electrolyte-based and solid polymer electrolyte-based ASSLIBs, respectively.

4.2.2 Requirements of Cathode Active Materials As relayed by Julien et al. [47], a key limitation in the overall performance of LIBs is governed by the inherent chemistry of the active materials in either the cathode or anode. These electrode active materials undergo electrochemical reactions involving the property (electronic, volume, etc.) manipulating the process of intercalation. A typical example is the layered compounds that are considered as prototypes in which Li+ ions are inserted into or extracted from the crystal structure. With many review publications having been written on this unusual chemical reaction, with an emphasis on its effects on the electronic and structural properties of the host electrode material [48–50], researchers were able to elucidate this phenomenon’s effect on

4 Prospective Cathode Materials for All-Solid-State Batteries

89

graphite [51], succeeded by layered transition-metal dichalcogenides (TMDs) [52– 54], and ultimately the layered oxides such as LiCoO2 that were used in the first commercialized LIBs as CAMs [55]. This has led to graphite and transition-metal oxides (TMOs) being the most studied Li+ ion intercalation compounds as these electrode materials are able to accept charge transfer. This is especially true for transition-metal cations because they can undergo redox reactions with insignificant changes in their coordination number; without major changes in the host enables it to basically retain its structural and compositional integrity [56]. Even though the words “intercalation” and “insertion” are usually used interchangeably, the structure of the host electrode materials can be used to appropriate the use of these two terms. The “intercalation” term can be reserved for the introduction of ions or molecules into the structure of a host lamellar compound, which is a compound with two-dimensional (2D) layers, as shown in Fig. 4.3b, in which the atoms share strong covalent or ionic bonds, while the layers are held in place by the week der Waal’s interactions [57]. The term “insertion” can then be used to describe the introduction of ions or molecules into one-dimensional (1D) and threedimensional (3D) structured compounds as illustrated in Fig. 4.3a and b, respectively [47]. All the same, for the intercalation/insertion reaction to take place, there are two main requirements that be met, which are [47]: i. A geometric structure that allows for easy access for the inserted ions or molecules to reach the vacant sites of the host lattice. ii. Accommodation of the exchanged electrons by providing an energetic condition with process complementary electronic states. As a result, a “mixed-conductor” behaviour is observed for most of the intercalation compounds, to some degree conducting both electrons and ionic species. The charge transfer in this case happens between the intercalant species and the host structure; this charge transfer process is a key enabler of the intercalation reaction and it is one of the fundamental features sought from an ideal cathode active material [47].

Fig. 4.3 The types of insertion compounds as a function of the dimensionality. Red circles are intercalated ions across the host channels [47]. Reproduced with permission from Ref. [47]. Copyright Springer

90

M. S. Ratsoma et al.

Overall, in accordance with sentiments alluded by Whittingham [46] and Julien et al. [47], an ideal cathode active material should possess key features as listed below. The various energy densities and storage capacities of several CAMs are illustrated in Fig. 4.4. (i) (ii)

(iii)

The host material should contain an ionic species that is willing to undergo redox reactions, ideally a transition metal. The insertion compound Lix My Xz (X = anion) should be able to provide a high lithium chemical potential (μLi(c) ) so as to maximize the cell voltage, i.e., the transition metal ion Mn+ in the host compound should exist in a high oxidation state. The insertion compound Lix My Oz should be able to maximize the cell capacity by allowing a large influx/departure of lithium x. This is a function of the number of available lithium sites and the availability of multiple valences for M in the host material.

Fig. 4.4 a Theoretical and practical gravimetric energy densities [8], and theoretical b gravimetric and c volumetric charge densities of several electrode materials for lithium-ion batteries [5]. Fig. 4(a) reproduced with permission from Ref. [8]. Copyright Elsevier

4 Prospective Cathode Materials for All-Solid-State Batteries

91

The host material should react with the Li+ ion in a reversible manner, with little to no change in the structure of the host during the overall extraction/insertion of x lithium so as to provide the cell with good cycle stability. (v) The host compound should be able to minimize polarization losses during the discharge/charge in order to provide high current density and power density. Thus, the material should possess excellent electronic (σ e ) and Li+ ion (σ Li ) conductivity. (vi) The insertion material should have a rapid reaction with the Li+ ion on both insertion and removal as this leads to a high power density. This can enable the battery to be comparable to the Ni/Cd battery, as well as find application in hybrid electric vehicles (HEVs) for regenerative braking energy storage. (vii) The insertion compound should display chemical stability during the Li+ ion extraction/ insertion process to avoid undergoing any reaction with the electrolyte. (viii) The CAM should exhibit an electrode potential that lies within the band gap of the electrolyte to avert any unwanted oxidation or reduction of the electrolyte throughout the entire charging/discharging process. (ix) The insertion compound should be cost-effective, environmentally friendly, and lightweight in order to be commercially sensible. (iv)

4.3 Cathode Material for ASSLIB 4.3.1 Lithium Transition Metal Compounds (Lx My Xz ) 4.3.1.1

Lithium Transition Metal Oxides (LTMOs)

Over the years lithiated transition metal oxides have been demonstrated as the most promising CAMs with enormous potential for structural improvements to afford LIBs with a long cycling life. This class of materials includes the LiMx Oy compounds (M = Co, Ni, Mn, etc.) and the related derivatives that include the metal substituted LiMM'O2 compounds (M' = 2 + or 3 + cations of Co, Ni, Mn, Cr, Fe, Al, etc.), the solid-solutions LiMxOy-LiM'xOy [52]. In this section we discuss the feasibility of some lithium transition metal oxides for the application as CAMs in ASSLIBs. (a) LiCoO2 Lithium cobalt oxide, LiCoO2 (LCO), is the most used CAM in commercial LIB technology, and also one of the most studied electrode materials [5, 55, 58–61]. As one of the ternary layered LTMOs, LCO normally forms the α-NaFeO2 -type crystallographic structure that belongs to R 3 m(D3d 5 ) space group. This is a derivative of the rock-salt (NaCl) structure with stacking of Li ions between adjacent MO2 slabs, i.e., the Mn+ and Li+ ions are occupying the alternating (111) planes, as illustrated in Fig. 4.5a [62, 63]. The thermodynamically stable O3-LiCoO2 lattice has been the

92

M. S. Ratsoma et al.

Fig. 4.5 a Crystal structure of layered LiMO2 (blue: transition metal ions; red: Li ions) [8], b Crystal structures of P2-, P3-, O2-, and O3-type LiMO2 . The “O” signals an octahedral coordination of the cation and the number represents the number of layers within a unit cell. Each layer in O3-type is related to the others by translation, whereas there is a 60° rotation in every second layer in O2-type [47]. Reproduced with permission from Refs. [8, 47]. Copyright Elsevier and Springer

preferred LCO structure for commercial use because it is much easier to prepare than its O3-LiCoO2 counterpart, although the electrochemical performance of the latter lattice is comparable to that of the former [64]. The labels “O2” and “O3” represent an octahedral Li environment in both cases, but a difference arises from the stacking sequences of the oxygen layers, i.e., ABCB and ABCABC sequences that lead to hexagonal unit cells with two and three sets of Co and Li layers, respectively (see Fig. 4.5b) [47]. The oxygen anions have been omitted in Fig. 4.5a to avoid ambiguity [8]. Two different LCO polymorphs have been prepared using a wide range of techniques in order to tailor the CAM to desired morphology, size (from micron to nanometer), and grain distribution size, which are important factors in the development of cathode materials with high efficacy. A rhombohedral structure, designated as HT-LCO, was obtained at high-temperature T > 850 °C, while a low-temperature phase spinel structured LT-LCO (Li2 Co2 O4 ) was synthesized at around 400 °C [65]. This classification mannerism for the two polymorphs is based on the formation of LiCoO2 using solid-state reactions at high (HT) and low (LT) temperatures. On the other hand, the HT-LCO polymorph has also been prepared at temperatures similar and even, respectively, lower than those of LT-LCO. For instance, Shao-Horn’ group observed the nucleation of LT-LCO from an intermediate Lix Co1-x [Co2 ]O4 spinel product before it underwent a very slow conversion to HT-LCO when they probed the stability of the spinel polymorph at 400 °C [66]. Chang et al. [67] prepared HT-LCO from reflux reactions at 130–200 °C. In addition, the two HT- and LTLCO polymorphs can also be obtained as thin films and fine grains with narrower size distribution using techniques such as RF Sputtering, sol–gel synthesis, chemical vapour deposition (CVD), pulsed laser deposition, combustion synthesis, molten

4 Prospective Cathode Materials for All-Solid-State Batteries

93

salt synthesis, mechanical activation, freeze-dried salt synthesis, and microwave synthesis [5, 47]. Shiraki et al. [68] demonstrated the preparation of orientation controlled LiCoO2 epitaxial thin films deposited on (110)-2 × 1 reconstructed surfaces of Au and Pt using pulsed laser deposition for application as CAMs in ASSLIBs. The epitaxial LCO thin films were observed to have CoO2 layers that are tilted with respect to the {111} plane of the Au and Pt support surfaces, which is suited for Li+ ion insertion/extraction reactions. When applied as cathode materials in ASSLIBs comprised of thin film lithium anode and LiPON solid electrolyte, the CAMs, the epitaxial films displayed improved electrochemical properties in the ASSLIBs compared to the batteries using liquid electrolyte. The LCO CAM exhibits excellent cyclability at room temperature, and hence the specific capacity of the electrode material is limited to the range of 137 to 140 mAh g-1 , although the theoretical capacity is reported at 273 mAh g-1 [69]. The shortfall of the practical specific capacity of the LCO material from the theoretical can be ascribed to the instability inherent to the LCO structure when more than half of the initially inserted Li ions are extracted. In addition, On the other hand, the highly toxic and expensive Co ions impact negatively on the application of LiCoO2 as CAM in LIBs because it introduces environmental problems and confers a high cost on the LIB device [4, 8]. Nevertheless, LCO has continued to enjoy some attention due to its good electrochemical properties and convenient synthesis, evidenced by the numerous reported literature employing it as a prototype CAM for solid–solid interface and interfacial modification [26, 31, 33, 70–82]. Lu et al. [78] demonstrated the enhancement of the electrochemical performance of a LCO cathode for ASSLIBs by coating with crystallinity and composition regulated LiNbO3 . Although an uncoated sample of LCO could reach initial charge and discharge specific capacities of 171.2 and 154.7 mAh g-1 at 0.1 C, respectively, a LiNbO3 -coated LCO that was calcined at 600 °C displayed a 91.2% Coulombic efficiency. The latter CAM further showed a high discharge capacity of 105.5 mAh g-1 at 1 C, as well as a high capacity retention of 78.0% after 2000 cycles at 0.5 C. The structural and morphological studies of the work are illustrated in Fig. 4.6, while the electrochemical characterizations are illustrated in Fig. 4.7. (b) LiNiO2 Lithium nickel oxide, LiNiO2 (LNO), is isostructural to LCO and also exists in both the cubic and the electrochemically active layered hexagonal structure [47, 79, 80]. The existence of the high lithium chemical potential (μLi(c) ) Ni3+ /Ni4+ cation couple in the LNO system provides a high cell voltage of approximately 4 V like LiCoO2 . However, Lix NiO2 shows a higher reversible capacity compared to Lix CoO2 due to the former offering a slightly higher amount of lithium that can be extracted and intercalated during the redox cycling processes, i.e., 0.55 for LNO to 0.5 for LCO. This allows the specific capacity of LNO to exceed 150 mAh g-1 with optimal cyclability [81]. Furthermore, nickel is slightly less expensive and less toxic than cobalt, which should make the LNO system more favourable for application in commercial LIBs.

94

M. S. Ratsoma et al.

Fig. 4.6 A SEM and surface EDS mapping images of a bare LCO, b LCO@1LNO- 400, c LCO@1LNO-500, d LCO@1LNO-600 and e LCO@1LNO-700 materials. f XRD patterns of five LCO materials. B Cross-section HRTEM and EDS mapping images of an LCO@1LNO precursor particle. C Schematic drawing of the crystallinity and composition change of coating layer in LCO@1LNO materials with different calcination temperature [78]. Reproduced with permission from Ref. [78]. Copyright Elsevier

On the other hand, despite the abovementioned fairly reasonable attributes of the LNO CAM, its implementation in commercial LIBs is hindered by several drawbacks encountered during the synthesis process. The main challenge is the difficulty in synthesizing LiNiO2 with all the nickel ions occurring in the Ni3+ valence state and crystallized in a perfectly ordered phase without a mixing of cations Li+ and Ni2+ ions in the interlayer space. A stoichiometric deviating structure is formed in which the Li-Ni–O system is represented by Li1-x Ni1+x O2 , or more explicitly [Li1- xNix]3b [Ni]3a O2 , where 3a and 3b are the site occupancy into the intra- and interlayer space, respectively [82–84]. Other problems include the tetragonal structural distortion (Jahn–Teller effect) associated with the low spin Ni3+ :d7 (t 2g 6 eg 1 ) ion [58], the irreversible phase transitions taking place during the charging/discharging process [85], as well as the exothermic evolution of oxygen at elevated temperatures and safety concerns in the charged state [86]. In addition, the LNO material is prone to cycle life failure when LNO with low lithium content (Lix NiO2 , x < 0.2) is formed during the charging process. The low lithium content material becomes highly catalytic towards oxidation of the electrolyte with some of the nickel ions likely to migrate to lithium sites. Hence, LNO was also

4 Prospective Cathode Materials for All-Solid-State Batteries

95

Fig. 4.7 A Electrochemical performances of bare LCO and LCO@1LNO cathodes for ASSLBs in the voltage range of 2.1–3.68 V (vs. Li–In). a Initial charge/discharge curves at 0.1 C, b rate performance curves, c cycle performance curves at 0.5 C. B a Electrochemical impedance spectroscopy of bare LCO/LGPS, LCO@1LNO-600/LGPS mixtures after standing different time (bare LCO, LCO@1LNO-600:LGPS ¼ 1:1, mass ratio). b The curves of the impedance value versus standing time. C Electrochemical impedance spectroscopy of ASSLBs using bare LCO and LCO@1LNO600 cathodes before and after cycled. Test temperature is 35 °C. D Schematic drawing of the chemical and electrochemical side reaction process between layered oxide material and sulphide electrolyte [78]. Reproduced with permission from Ref. [78]. Copyright Elsevier

demonstrated to be thermally unstable in its charged state [87]. Pristine LNO is difficult to synthesize due to the presence of NiII (in some instances reaching up to 2%) between the NiO6 layers. In fact, the presence of NiII between the NiO6 layers is considered as the main source of the irreversibility during the first chargedischarge cycle. These NiII species usually require an extra charge in order to be oxidized to a higher valency state [88], when electrolyte decomposition is controlled. The stability of the LNO material during the charging process can be improved by partial substitution of Ni ions with redox inactive dopant materials such as B and Al [47, 89, 90]. Moreover, the overall improvement of the performance of LNO is achieved through derivatives of the materials, i.e., transition metal substitutions and solid-solutions with other CAMs, which is covered in Sect. 1.3.1.1 (d). Nonetheless, the preparation of LNO usually follows similar methods as LCO. Kim, Seong and Yoon synthesized LNO cathode material for application in all-solid-state thin film batteries. The LNO was grown through radio frequency (rf) reactive sputtering and subsequently annealed at 700 °C. Structural characterization studies showed the synthesized film had very fine grains with a crystalline structure. The LNO-based thin-film ASSLIB was able to reach a specific capacity of about 57 μAh/cm2 μm, as well as an initial discharge capacity of 65.3 μAh [91]. (c) LiMn2 O4 The 3D lithium manganese oxide, LiMn2 O4 (LMO), which has a cubic spinel-like structure as illustrated in Fig. 4.8a, is the most studied lithium manganate [47], as

96

M. S. Ratsoma et al.

well as the third-most-popular CAM [61], which drew much attention is a prospective replacement for LCO. The crystal structure of LMO possesses the symmetry Fd3m and is represented by the general structural formula (A)8a [B2 ]16d O4 , where the B cations are located at the octahedral 16d sites, the oxygen anions are found at the 32e sites and the A cations at the tetrahedral 8a sites. The oxide ions, which are arranged in a quasi-cubic close-packed (ccp) array, integrate MnO6 octahedra and LiO4 tetrahedra that share two opposite corners. In general, the spinel structure is characterized by the respective structural groups in the following manner: (i) a 3D framework of MnO6 octahedra connected to each other through edge sharing, (ii) tetrahedral structures of LiO4 that are connected to a different MnO6 at each of their four corners, but essentially isolated from one another, and (iii) a 3D host network of octahedral (16c) and tetrahedral (primarily 8a) sites, with lithium-ions able to move through the (1 × 1) channels of the spinel lattice [92]. Illustrated in Fig. 4.8b and c are the atomic arrangements of the normal (Fd3m S.G.) and ordered (P41 32 S.G.) spinel lattices, respectively.

Fig. 4.8 a Crystal structure of spinel LiM2 O4 (blue: transition metal ions; red: Li ions) [8], Schematic representation of the structure of LiM2 O4 spinel lattices, b the smallest (primitive) cubic unit cell of normal spinel (Fd3m S.G.), and c the unit cell of the 1:3 ordered spinel (P41 32 S.G.). The structure is composed of alternating octants of LiO4 tetrahedra and M4 O4 cubes to build the fcc unit cell [47]. Reproduced with permission from Refs. [8, 47]. Copyright Elsevier and Springer

4 Prospective Cathode Materials for All-Solid-State Batteries

97

When compared to LCO and LNO, LMO presents advantages of less toxicity, lower cost due to naturally abundant manganese, and a higher cell voltage. However, it is difficult to prepare samples of good quality, it is essentially prepared via methods similar to LCO. In principle, LMO allows for the intercalation/extraction of lithiumions in the range of 0 < x < 2, i.e., 0 < x < 1 at ~ 4 V and 1 < x < 2 at ~ 3 V [93]. When cycling at 3 V, LiMn2 O4 transforms to a tetragonal phase on the surface of the bulk cubic LMO. Moreover, LMO eventually suffers from a pronounced cooperative Jahn– Teller distortion as a result of the decrease in the average valence of manganese ions during intercalation of lithium-ions. This leads to the cubic spinel crystal structure becoming distorted tetragonal with a c/a ≈ 1.16, with 6.5% increase in the volume of the unit cell. The coexistence of the cubic and tetragonal phases inflict a problem on the performance of LMO due to the volume change associated with the structural transformation, which leads to a fading of the capacity [47, 61]. The high c/a ratio mentioned above restricts the specific capacity to 120–125 mAh g-1 , as well as resulting in a significant capacity degradation at moderate temperatures in the range of 50 to 70 °C [94]. Alternatively, when LMO is cycled at the 4 V region (0 < x < 1), the crystal lattice remains cubic with only a minimal volumetric change[95–97]. As a result of the minor volumetric change, a long cycle life can be obtained when cycling between 3.5 and 4.5 V, which is contrary to the significantly reduced cycle life brought on by the structural degradation of the electrode when cycling at lower potentials [5]. Consequently, only the 4 V region is most favourable to be applied for commercial LIBs, in which a reversible gravimetric capacity of 148 mAh g-1 can be obtained [98]. Over the years, the structural integrity and electrochemical performance of LMO materials were shown to be enhanced by fluorination [99, 100], coating with other active metal oxides [101–105], cationic substitution [106, 107], substituting some Mn3+ ions with Li+ [97, 108–110], as well as adopting the use of nano-structured particles [111]. On the other hand, a theoretical volumetric capacity reaching up to 650 mAh cm− 3 can be obtained using a spinel unit cell of Li8 Mn16 O32 , which has a volume of 550 Å3 [98]. Liang et al. [112] employed LMO as a cathode in a cell that exhibited excellent rate capability and long-term cycling performance, with an initial discharge capacity of 107.4 mAh g-1 and a 91.4% retention of the initial capacity after 200 cycles. Zhang’s group fabricated a high voltage, flexible and low-cost all-solid-state lithium battery with a wide working temperature range using LMO as a cathode [113]. The group’s main aim was to solve the capacity decay of the spinel LMO during cycling at elevated temperatures by using a SE. Structural analyses of the LMO powder showed the cathode material to be typical and pure spinel phase and shape. Galvanostatic charge/discharge tests of the Li/SE/LMO cell have conducted temperatures from 25 °C to 80 °C, with cycling between 4.3 V and 3 V at a current density of 50 mA g-1 . The cell showed an initial reversible capacity of 67 mAh g-1 , which was rather low compared to a liquid electrolyte-based counterpart cell. The lower capacity of the cell was ascribed to the relatively low conductivity of the SE. At 25 °C, the cell exhibited a stable cycling performance by achieving an 88% retention of the initial capacity after 100 cycles. It further showed high stability when cycled at 80 °C,

98

M. S. Ratsoma et al.

attaining a higher specific capacity of 80 mAh g-1 at a current density of 50 mA g-1 . Moreover, its capacity still remained at 50 mAh g-1 after 50 cycles, with a high Coulombic efficiency deduced by a capacity loss of about 0.75% per cycle from the initial capacity. The liquid electrolyte-based cell only manages one cycle at the said temperature. Studies of the cathode material’s structural integrity post-cycling at 80 °C in both cells showed revealed no changes to the spinel structure of LMO compared to pre-cycling, although a change in the intensity of LMO peaks was observed from XRD spectra of the cathode used in the liquid electrolyte-based cell, indicated a loss of active LMO caused by the side reactions of the electrolyte with the electrode. Using the SEM technique, the latter electrode material was also observed to have changed in surface morphology to having rough and fluffy particles, contrary to the smooth surfaces of the pre-cycling and solid-state battery cathodes. The loss of active LMO material was further confirmed by the lower peak intensities/areas observed from XPS spectra of the liquid electrolyte-based cell cathode, while those of the counterpart cycled cathode remained almost the same as the pre-cycling material. The structural, morphological and electrochemical observations of the study are presented in Figs. 4.9 and 4.10 (d) Derivatives of LTMOs The many drawbacks encountered with the use of LTMOs have led to researchers investigating derivatives of the said CAMs, with the ultimate goal being to improve their electrochemical performance. The derivatives are obtained through the introduction of dopants to the CAMs, partial substitution of M n+ ions, as well through solid solutions of the CAMs. In the case of LCO, dopants, such Al [114, 115], Mg [116], B [117], and Cr [118], were used to stabilize the layered lattice at x(Li) < 0.5 and to extend the specific discharge capacity of LiCo1-y M'y O2 system [119, 120]. The said dopants are generally introduced via soft-chemistry using the dicarboxylic acid-assisted sol–gel method [121, 122]. An example is the boron-substituted LCO (LiCo1-y By O2 ), in which the layered structure is preserved upon doping of a large amount of BIII (y ≤ 0.25) with no detection residual impurity phases [117]. In this doped LCO (d-LCO) optimal electrochemical properties are obtained at a composition approaching the limit of solubility of boron. An improved cycling performance of the battery is observed at y(B) ≤ 0.2 due to the dopant’s inclination to lattice adaptation to the insertion/extraction of Li+ ions, as well as playing a role of off-setting the initiation of the structural first-order transition associated with the Verwey transition in Li0.5 CoO2 . Improvements in the electrochemical performance of LNO are obtained through preparation of Ni-rich solid solutions of LiNi1-y Coy O2 (NCO). The NCO systems have led to successful results, with focus being given to overcoming the capacity fading by doping with several cations; even though at a lesser extent, cationic mixing was observed to still exist [116, 123–126]. Stabilization of the layered structure, enhancement of the electrochemical capacity and the reversibility of the charge– discharge process are realized as evidence and consequence of the effect of reducing the amount of Ni3+ present in the 3a sites by the introduction of even a small amount of Co. The performance of LiNi1-y Coy O2 CAM could be expected to give a similar to that

4 Prospective Cathode Materials for All-Solid-State Batteries

99

Fig. 4.9 a The XRD pattern of LMO powder, b SEM of LMO powder, c the charging/discharging curve of PVDF all solid-state battery at 25 °C, d the cycle curve of LMO/PVDF all-solid-state battery at 25 °C, e the charging/discharging curve of liquid LMO battery at 80 °C, and f the cycle performance of PVDF solid battery at 80 °C [113]. Reproduced with permission from Ref. [113]. Copyright John Wiley and Sons

of LCO since the voltage-composition curves for LCO and LNO are similar, although the NCO system presents a significant reduction of cobalt and partial elimination of the NiII species from the lithium layers for y > 0.3. A rather larger capacity is expected for the NCO system due to the Ni4+ /Ni3+ couple lying about 0.35 eV above the Co4+ /Co3+ couple [127]. The specific capacity of a NCO system with partial substitution of Co by Ni increases to about 180 mAh g-1 from the specific capacity of LCO of about 130 mAh g-1 , although the increase is accompanied by a slight decrease in the discharge voltage. The NCO system is shown to be a replacement for LCO [47].

100

M. S. Ratsoma et al.

Fig. 4.10 XRD spectra of LMO electrode a before cycling, b cycled in solid-state batteries after 50 cycle at 80 °C, c cycled in liquid electrode at 80 °C, the SEM images of LMO electrode d before cycling, e after cycling in solid-state electrolyte at 80 °C, f after cycling in liquid electrolyte at 80 °C. the XPS images of LMO electrode g before charging, h after cycling in solid electrode electrolyte at 80 °C and i after cycling in liquid electrolyte at 80 °C, and the impedance of LMO battery at 80 °C in j liquid LMO battery before cycling and after failure and b all solid-state LMO battery before cycling and after 50 cycles [113]. Reproduced with permission from Ref. [113]. Copyright John Wiley and Sons

Amongst the Ni-rich layered compounds, the aluminium-doped NCO, LiNi1-y-z Coy Alz O2 (NCA), exhibits enhanced electrochemical performance due to its greater structural and thermal stability in comparison to the non-Al-doped NCO materials [123, 128, 129]. Doux et al. [130] studied the effect of the stack pressure on the cycling stability of an all solid-state battery employing LiNbO3 -coated NCA

4 Prospective Cathode Materials for All-Solid-State Batteries

101

(LiNi0.80 Co0.15 Al0.05 O2 ) as a cathode which is essential for ensuring optimum contact between the electrodes and the solid electrolyte. Yin’s group [131] investigated the effect of Li10 GeP2 S12 and Li3.25 Ge0.25 P0.75 S4 solid electrolytes on the rate and low temperature performances of on NCA (LiNi0.8 Co0.15 Al0.05 O2 ) cathode materials allsolid-state lithium batteries. The NCA cathode in the Li10 GeP2 S12 -based cell showed enhanced capacity and cyclability, with a reversible capacity of 107.2 mAh g−1 and a capacity retention of 87.1% after 30 cycles. These results were higher than that of NCA cathode in the Li3.25 Ge0.25 P0.75 S4 -based cell (81.9 mAh g−1 , 72.1%). The layered, monoclinic LiMnO2 , which is isostructural with LCO, tends to transform on cycling at 3–4 V versus Li0 /Li+ to the more thermodynamically stable spinel phase. Cation doping (e.g., Ni2+ or Cr3+ ) has been shown to successfully stabilize the layered phase. The nickel substituted layered oxide LiNi0.5 Mn0.5 O2 (NMO), which crystallizes in a hexagonal unit cell (α-NaFeO2 -like), was reported to be a promising cathode active material for LIBs [132, 133]. Cationic species of nickel and manganese in the NMO system assume the 3 + and 4 + oxidation states, respectively, with a minute presence of the divalent Ni2+ ions. The presence of the manganese ions in the + 4 oxidation state bestows stability on the hexagonal structure to overcome the instabilities brought on by the Jahn–Teller distortion-prone Mn3+ ions. When compared to LMO, NMO demonstrates greater capacity, with a reversible specific capacity of 150 mAh g-1 when cycling in the voltage range 2.5–4.3 V. It also shows greater thermal stability than LNO. Considered as simple solid solution of LiCoO2 -LiNiO2 -LiMnO2 , the Li(Ni,Mn,Co)O2 (NMC) system boasts the promise of enhanced thermal and structural stability, as well as the considerable increase in the capacity retention due to the combination of nickel, manganese, and cobalt. Liu’s group pioneered the NMC chemistry in a bid to develop high-power lithium-ion batteries that possess an extended calendar life and thermal robustness which could replace the LCO-based batteries [134]. Despite having impressive electronic conductivity, the lamellar NMC compounds, which crystallize with the α-NaFeO2 -type structure (R 3 m space group), suffer from poor cycling stability at a high rate or high cut-off voltage, restricting their use to portable applications. Having linked the capacity retention efficacy of the CAM to the surface chemistry of the particles, many attempts have been made to protect the surface of NMC materials from the effects of the SEI by coating with metal oxides such as Al2 O3 , TiO2 , ZrO2 , and MgO, or other compounds such as FePO4 , LiFePO4 , and Li4 Ti5 O12 . Several NMC systems with different compositions have been developed and studied for their structural integrity and electrochemical performance. Shaju’s group profiled the electrochemical performance of LiNi1/3 Mn1/3 Co1/3 O2 , which showed a specific capacity of 160 mAh g-1 over 2.5–4.4 V [135]. The hexagonal structured NMC having a wonderful composition of LiNi1/3 Mn1/3 Co1/3 O2 has in recent times received much attention as a prospective cathode material as a consequence of its good stability during cycling even at high temperatures, as well as its high reversible capacity [136]. The lithium-rich NMC cathode, Li1+x (Ni1/3 Mn1/3 Co1/3 )1-x O2 , demonstrated enhanced cyclability and rate capability compared to the stoichiometric material up to a 4.6 V cut-off charge voltage (vs. Li0 /Li+ ) [137–139]. Iwasaki et al.

102

M. S. Ratsoma et al.

Fig. 4.11 Initial charge–discharge curves of all-solid-state battery (Li/LiPON/LATP-sheet/NMCcomposite-film by the NMC-30/Pt) at 298 K (blue) and 333 K (red). I = 5 mA cm-2 . The inset shows the cross-sectional SEM image around the composite film electrode/LATP-sheet interface [140]. Reproduced with permission from Ref. [140]. Copyright Elsevier

[140] prepared thick films of LiNi1/3 Mn1/3 Co1/3 O2 via aerosol deposition using NMC powder (D50 = 10.61 mm) as source material for application as CAMs in all solidstate batteries. The as-assembled solid-state battery showed an active material-basis discharge capacity of 152 mAh g-1 at a scanning rate of 0.025 C between 3.0 and 4.2 V at 333 K, while a niobium oxide coated NMC composite electrode showed initial discharge capacities of 87 and 138 mAh g-1 at 298 and 333 K, respectively, illustrated in Fig. 4.11. Phillip and co-workers investigated the structural degradation of high voltage Ni-rich NMC cathodes in solid-state batteries [141]. The study showed the SE could not fully prevent the decomposition of NMC from occurring but was only able to suppress the extent of degradation. The capacity of the solid-state cell was observed to decrease from 203 to 93 mAh g-1 in the first cycle and from 93 to 79 mAh g-1 over the subsequent 99 cycles.

4.3.1.2

Polyanionic Lithium Transition Metal Compounds

Recently, polyanion-based compounds, Lix M y (XO4 )z ( X = P, S, Si, Mo, W, etc.), have received considerable interest for application as low cost and high safety CAMs in secondary lithium batteries [142–144]. Stand out CAMs in this family of electrode materials is the olivine structured lithium metal phosphates (LiMPO4 ). The former have gained much attention due to the inherent stability of the polyanion group that is able to delay or minimize the loss of oxygen that usually occurs with the oxidebased insertion compounds [8]. Thus, in this section we limit our discussion to the LiMPO4 compounds. We also look at the fluorinated polyanionic lithium transition

4 Prospective Cathode Materials for All-Solid-State Batteries

103

metals compounds, which have been demonstrated to possess features such as highvoltage redox reactions, stabilization of the host lattice, inherent protection from acid attack and electrolyte decomposition, and easy mobility of Li+ ions [145–150]. (a) LiMPO4 Lithium metal phosphates have gained considerable interest as prospective cathode active materials and since have found application in modern commercial rechargeable batteries because of their high gravimetric capacity and relatively low cost. This class of olivine materials crystallizes in an orthorhombic structure, modelled by the structure of LiFePO4 in Fig. 4.9. Lithium iron phosphate, LiFePO4 (LFP), remains the most frequently used lithium metal phosphate, although there have been various reports profiling the efficacy of the cobalt- and manganese-based (LiCoPO4 and LiMnPO4 ) compounds as potential LIB CAM. The LiFePO4 CAM has received the most interests as it possesses several advantages that include the clean and abundant nature of iron phosphate, a fairly high gravimetric capacity (170 mAh g-1 ), a reversible of lithium storage, high thermal stability, low cost and high safety [142]. The structure of LiFePO4 consists of a distorted hexagonal-close-packed (hcp) oxygen framework covering Li and Fe ionic species located in half the octahedral sites, as well as P ions in one-eighth of the tetrahedral sites [151]. The LiO6 and FeO6 octahedra are edge and corner shared, respectively, whereas both run parallel to the c-axis and alternate in the b direction. The PO4 tetrahedra bridge the a-c planes that contain the Li atoms. The preparation of LFP usually follows methods such as solid-state reactions, hydrothermal methods, co-precipitation methods, microwave synthesis, polyol and solvothermal processes, micro-emulsion, spray pyrolysis, template techniques, and mechanical activation [47]. The LFP (Lix FePO4 ) cathode material is usually cycled between 0.1 < x < 1 and attains a stable reversible charge/discharge at a rather voltage of about 3.4 V. The theoretical gravimetric storage capacity of LFP can reach up to 152.9 mAh g-1 as a result of its low molecular weight, while the volumetric capacity is less exciting, i.e., a maximum volumetric capacity of 610 mAh cm-3 is likely to be obtained when an olivine unit cell consisting of Li4 Fe4 P4 O16 with a unit-cell volume of 291 Å3 is used in cycling all the lithium [5, 152]. Adding carbon to the LFP matrix [153], as well as coating a thin layer of carbon onto the surface of LFP particles [154, 155], has become a common practice in the production of the said CAM in order to increase the electronic conductivity. This carbon-coating practice was demonstrated to effect a seven-order-of-magnitude increase in the electronic conductivity of LFP when carbon was introduced on the CAM via addition of sucrose using a spray pyrolysis technique [156]. In general, the addition of carbon confers better electronic conductivity onto LFP, and consequently giving it a high rate capability and a high capacity. Ait-Salah’s group reported a gravimetric capacity of about 160 mAh g-1 from a LiFePO4 sample that was coated with 1 wt% carbon [157] (Figs. 4.12 and 4.13) Wu et al. [158] presented a first design of a completely different solid-state cointype half-cell built with LiFePO4 as a cathode material, Li metals as the anode and a novel quasi-solid-state composite electrolyte termed as ternary nanocomposite electrolyte (TNCE). The Li/TNCE/LiFePO4 cell was able to demonstrate excellent

104

M. S. Ratsoma et al.

Fig. 4.12 Crystal structure of LiFePO4 olivine [47]. Reproduced with permission from Ref. [47]. Copyright Springer

Fig. 4.13 a Impedance spectra of the Li/TNCE/LiFePO4 cell before charging/discharging at different temperatures, b Charge–discharge curves of cells at three temperatures, c and d cycling performance of cells at 40° C and 55° C, respectively (Insets: Impedance spectra of cells discharged to 2.5 V after selected cycles at the two operating temperatures), e cyclic voltammograms of the Li/TNCE/LiFePO4 cell at different scan rates, and f initial discharge curves and specific capacity versus cycle number (inset) of the Li/TNCE/LiFePO4 cell at different discharge rates at 30 °C. Reproduced with permission from Ref. [158]. Copyright John Wiley and Sons

4 Prospective Cathode Materials for All-Solid-State Batteries

105

thermal stability, showing even better charge–discharge performance at high temperatures compared to ambient. A sub-cooling phenomenon was also observed when the cell was cooled back to ambient temperature. Upon cycling at different temperatures, the cell displayed a satisfactory discharge capacity of 133.4 mAh g-1 after the ninth cycle at 25 °C, while it showed a discharge capacity of 155.2 mAh g-1 as the maximum at 55 °C. The group proclaimed an observation of a directly proportional effect that an increasing temperature has on the capacity and the Coulombic efficiency, as well as its inverse impact on the polarization between the charge and discharge plateaus. Showing reproducible cycling with excellent Coulombic efficiency at 40 and 55 °C, the cell showed an initial discharge capacity of 148.8 mAh g-1 at 40 °C with a gradual increase over 10 cycles due to the activation of the cell, as well as maintenance of a high Coulombic efficiency approaching 100% over 50 cycles. A higher initial capacity of 154.0 mAh g-1 was observed at 55° C. Overall, cell was able to show an acceptable rate capability with the maximum discharge capacity reaching of 138.5 mAh g-1 at a scanning rate of 0.2 C at 30 °C. The authors ascribed the results to the faster ion transfer in the TNCE and easier Li+ ion extraction/insertion into the LiFePO4 crystalline structure, as well as retention of their structural integrity after cycling. The electrochemical studies of the work are illustrated in Fig. 4.10. Yan et al. [159] used LFP as a cathode material in exploiting the electrochemical properties of an ultrathin nanoscale solid electrolyte, Li7 La3 Zr2 O12 (LLZO). With Li metal as the anode, the Li/LLZO/LFP cell displayed an initial discharge capacity of 160.4 mAh g-1 , which was 94.4% of the theoretical capacity of LFP. The cell further achieved a discharge capacity of 136.8 mAh g-1 after 100 cycles. A more stable electrochemical performance of the cell was observed at 60 °C, showing a similar trend observed by Wu’s group regarding the impact of a raised temperature on the performance of the cell. The cell displayed a discharge capacity of 146.2 mAh g-1 after 100 cycles at a scan rate of 0.1 C, which was 99.4% of the second cycle; only 0.06% (0.7 mAh g-1 ) of capacity was lost during cycles 2–100. (b) Fluorinated (LiMXO4 F)

Polyanionic

Lithium

Transition

Metal

Compounds

Polyanion-based insertion compounds are considered to have in recent times been considered as safe alternatives for the oxide-based electrodes, as these materials exhibit high Coulombic efficiency on long-term cycling compared to lithium metal oxides, as well as no release of oxygen from the lattice or any side reactions with the electrolyte [47, 160]. Conversely, these materials suffer from poor electronic conductivity [143]. The introduction of fluorine to the CAM via replacing of oxygen by fluorine or coating the CAM particles with fluorine has been considered as an effective approach at improving the electrochemical and safety parameters of polyanionic insertion compounds. The fluorinated compounds have attracted growing interest due as a result of their high potential and thermal stability. In this section we discuss the structural properties, preparation methods and electrochemical performance of the fluorophosphates (Lix MPO4 F) and fluorosulphates (LiMSO4 F).

106

M. S. Ratsoma et al.

(i) Fluorophosphates (Lix MPO4 F) Crystalline materials comprised of tavorite framework-structured of Li-containing fluorophosphates of 3d-metals that are described by general formulae LiMPO4 F and Li2 MPO4 F (M = V, Fe, Ni, Co) have been the subject of studies focusing on developing new high voltage cathodes for lithium technology batteries [45, 161]. The tavorite structured materials in this family of compounds are a derivative class of the olivine structured compounds and inherently present many of the features of the olivine series. As shown in Fig. 4.14, the crystal structure of LiMPO4 F is comprised of lithium-ions surrounded by transition metal octahedra and phosphate tetrahedra (oxygen and fluorine atoms omitted for clarity). The strength of the phosphorus and oxygen bonds give the tavorite materials good thermal stability, but these materials suffer from low energy density. The existence of fluorine in the tavorite structure allows for Li+ ion diffusion through multi-dimensional pathways [8]. Typical compounds in this class of CAMs include LiVPO4 F, and LiFePO4 F. Lithium vanadium fluorophosphate (LiVPO4 F) is an intriguing cathode active material that has been demonstrated to possess high voltage, long cycle life, good thermally stability, and a stable crystalline structure [201–204]. It is considered as a 4 V cathode active material that is significantly safer than the oxide insertion materials. The tavorite structure crystallizes in a triclinic phase (P1 S.G.) in which its framework is comprised consists of V3+ O4 F2 octahedra connected by fluorine vertices that form (V3+ O4 F2 )∞ chains along the c-axis. The corner-sharing linkages of these chains with PO4 tetrahedra result in an open 3D lattice having pathways along the a, b, and c directions that can accommodate Li+ ions in either one of two sites. The first site, Li(1), is five coordinated with low occupancy (~18%), whereas the second site, Li(2), is six coordinated with high occupancy (~82%) on the 2i Wyckoff positions [47]. The said CAM is mainly prepared via carbothermal reduction method, but procedures such chemical lithiation reactions, sol–gel methods and post-annealing techniques can be used to synthesize the material [45]. The cathode active material was shown in preliminary electrochemical studies to demonstrate a reversible lithium Fig. 4.14 Crystal structure of tavorite LiMPO4 F (blue: transition metal ions; yellow: P ions; red: Li ions) [8]. Reproduced with permission from Ref. [8]. Copyright Elsevier

4 Prospective Cathode Materials for All-Solid-State Batteries

107

extraction/insertion reactions based on the V3+ /4+ redox couple. Firstly, this shows a discharge potential lying at about 4.19 V versus Li0 /Li+ ; Secondly, a two-phase charge transfer mechanism together with a phase nucleation behaviour; and Thirdly, a reversible specific capacity of ~ 115 mAh g-1 , which is approximated to cycling of x = 0.84 in Li1-x VPO4 F [8]. Lithium iron fluorophosphate (LiFePO4 F) has also found great attention for application as a cathode active material in LIBs. The CAM is rather unique compared to other insertion compounds as it is usually set up in the charged state and is then discharged to form Li2 FePO4 F [8]. It is essential for the synthesis of LiFePO4 F to be free of hydroxyl groups as this affects the material’s electrochemical reversibility. The high redox potential needed to oxidize Fe(II) to Fe(III) limits the complete extraction of Li+ ions from LiFePO4 F, hence LiFePO4 F is restricted to the effective accommodation of one Li+ ion per unit formula. Electrochemical testing has shown excellent capacity retention of about 150 mAh/g over 40 cycles even at elevated temperature [162]. Fluorosulphates (LiMSO4 F) The recently discovered electroactive lithiated fluorosulphates (LiMSO4 F) comprise a group of electrode materials that possess a good blend of features that cater for excellent electrochemical performance and reduced safety issues [47]. Depending on the nature of the transition metal ion, the crystal structures of fluorosulphates can take either of the three main phases that include the tavorite (M = Fe), triplite (M = Mn), or sillimanite (M = Zn). The main differences between the tavorite (P1 S.G.) and triplite (P1 S.G.) structures are illustrated in Fig. 4.15. Phase-pure tavorite LiFeSO4 F is difficult to prepare using typical solid-state methods because its low thermodynamic stability requires low temperature (< 400 °C) crystallization of the material in hydrophobic ionic liquids [163, 164]. Alternatively, Tripathi’s group demonstrated a facile route for the synthesis of a highly electrochemically active LiFeSO4 F material through reaction in hydrophobic tetraethylene glycol at 220 °C. The materials offer easy reversible Li+ ion insertion as the lattice has close structural similarities to that of the tavorite-type monoclinic FeSO4 F (C21 /c S.G.). The LiFeSO4 F CAM is readily oxidized to form the Li-free empty host FeSO4 F, however, the volume contraction from 182.4 to 164.0 Å3 is more pronounced than that of the olivine LiFePO4 framework [165]. Ionothermal (soft chemistry) synthesized LiFeSO4 F was shown to attain a reversible capacity 130 mAh g-1 at a C/10 rate involving the Fe2+ /Fe3+ redox reaction at 3.6 V versus Li0 /Li+ . A solid-state reaction was used to prepare triplite LiFeSO4 F which evolved from the tavorite phase in 6 days [166]. In the disordered triplite material, intercalation of the Li+ ions occurs at 3.9 V, a value that is 0.3 V higher than that of its ordered tavorite counterpart, ascribed by Ben-Yahia’s group to be a trait of the longer Fe–O bond length [167]. The group further attributed the voltage difference between the tavorite and the triplite phases to a result of the difference in the anionic networks of the two polymorphs. This difference was pin-pointed to the change in the electrostatic repulsions brought on by the configuration of the fluorine atoms around the transition-metal cations. Overall, the lithiated fluorosulphates present a

108

M. S. Ratsoma et al.

Fig. 4.15 Schematic representation of the crystal structures of the a triplite and b tavorite phases [47]. Reproduced with permission from Ref. [47]. Copyright Springer

set of attractive advantages which include the benefit of low-temperature synthesis from the abundant FeSO4 ·nH2O precursor [45].

4.3.2 Transition Metal Oxide (TMOs) and Dichalcogenides (TMDs) 4.3.2.1

Transition Metal Oxides (Mx Oy )

(a) Vanadium Oxide (Vx Oy ) The vanadium-based oxides have received much attention for application as CAM in lithium technology batteries due to their good electronic conductivity, excellent chemical stability, and high energy density [168]]. Vanadium oxides emerge with a promise of cathode materials with a wide range of capacities as they can exist in a number of oxidation states, from 2+ in VO to 5+ in V2 O5 [169]. One of the stand-out cathode materials in this group is the layered vanadium pentoxide (V2 O5 ), which has shown a promising electrochemical performance that is attributed to its high discharge capacities and good capacity retention [45]. Vanadium pentoxide is one of the earliest studied intercalations compounds that can exhibit numerous different phases with the intercalation of 3 Li+ ions per unit formula, Vanadium pentoxide adopts an orthorhombic unit cell crystal structure with that belongs to the Pmnm space group with lattice parameters a = 11.510 Å, b = 3.563 Å, and c = 4.369 Å [170, 171]. The orthorhombic crystal structure of V2 O5 is comprised of chains of edge sharing VO5 square pyramids, as shown in Fig. 4.16(a), of which the chains are connected through corner sharing. The vanadyl bond of the distorted polyhedra is measured at a short length of 1.54 Å, and four oxygen atoms located in the basal plane of the polyhedra at distances ranging from 1.78 to 2.02 Å (Fig. 16(b)).

4 Prospective Cathode Materials for All-Solid-State Batteries

109

The oxygen atoms coordinated to a vanadium atom are geometrically labelled O1 , O21 , O23 , O'23 , and O3 , respectively. In the deformed octahedron, which includes the O'1 atom, the V-O1 bond length is the shortest at 1.54 Å, whereas the V-O'1 is measured at 2.81 Å. The chains of the deformed octahedrons face the a-direction as a result of the octahedrons that share common corners in the b direction linking up at common edges. A number of synthetic methods have been employed to prepare V2 O5 , which include the sol–gel, solvothermal, RF sputter deposition, pulsed laser deposition, chemical vapour deposition, atomic layer deposition, precipitation, and electrodeposition methods [5, 45]. Pomerantseva et al. [172] proposed a novel approach to synthesize nanostructured V2 O5 thin films by biotemplated synthesis using Tobacco mosaic virus particles. When V2 O5 undergoes electrochemical cycling, two sharp peaks are observed at 3.2 and 3.4 V, of which the underlying electrochemical reactions are ideal for reversible Li storage. The amount of Li that can be intercalated in this region varies between 0 < x < 0.8 for Lix V2 O5 [173]. Cycling at lower potentials reveals a third response at 2.3 V. This region allows for intercalation of lithium content of up to x = 2, however, the phase transformation occurring from this process is irreversible [174]. Thus, V2 O5 is generally never intercalated beyond x(Li) = 0.8, which results in a theoretical maximum specific capacity of 118 mAh g−1 , well as a volumetric capacity of 400 mAh cm−3 , considering a volume of 90 Å3 per V2 O5 unit [175]. Zhang et al. [176] assembled an all-solid-state lithium battery using reduced graphene oxide (rGO) supported V2 O5 nanowires as a cathode, a solid polymer electrolyte [PEO-MIL- 53(Al)-LiTFSI] and Li metal as an anode. The battery was able to show a fast and stable lithium-ion-storage performance in a wide voltage window of 1.0–4.0 V versus Li+ /Li at 80 °C, achieving a discharge capacity of 320.5, 343.5,

Fig. 4.16 a Projection of the layered structure of V2 O5 on (001). Superimposed oxygen atoms are symmetrically displaced. b The deformed pyramid of the V2 O5 structure, shown with the coordinate system and labels of V, O1 , O21 , O23 , and O3 atoms. The solid and dashed lines schematically represent the chemical bonds, and numerical values indicate the bonding length (Å) between atoms. The O'1 atom is the O1 -type atom belonging to the neighbour pyramid painting at opposite direction. Reproduced with permission from Ref. [47]. Copyright Springer

110

M. S. Ratsoma et al.

Fig. 4.17 a TEM and b HRTEM images of V2 O5 nanowires. The inset shows the FFT analysis. c Photograph showing the self-supported flexible rGO/V2 O5 composite paper under a bent state. d SEM image of the rGO/V2 O5 composite paper [176]. Reproduced with permission from Ref. [176]. Copyright ACS

and 299.5 mAh g-1 after for the 2nd , 20th , and 40th cycles at a current density of 17 mA g-1 , respectively. These capacities showed the successive phase transformations from α-V2 O5 to ε-Li0.5 V2 O5 to δ-LiV2 O5 to γ-Li2 V2 O5 after the first cycle. The battery displayed average discharge and charge capacities of 329.2 and 343.8 mAh g-1 after 40 cycles, respectively, with the Coulombic efficiency remaining stable near 99%. The authors ascribed the excellent electrochemical performance to the integration of the electronic conductivity of rGO and interconnected networks of the V2 O5 nanowires and solid electrolyte (Figs. 4.17 and 4.18).

4.3.2.2

Transition Metal Dichalcogenides (Mx Xy , X = S, Se)

Recently, transition metal dichalcogenides (TMDs) have become popular for application as electrode material in numerous energy storage and conversion technologies because of their superior physical and chemical properties [177]. The TMDs were used as cathode material in the early reported rechargeable lithium batteries, even though initial interest in these intercalation compounds was driven by their superconducting properties at very low temperatures [178]. The layered structure of TMDs is comprised of a sheet of metal atoms (M) covalently sandwiched between two sheets of chalcogen atoms (X). The X-M-X interlayers are held in place by the weak van der Waal’s forces and each sheet is made

4 Prospective Cathode Materials for All-Solid-State Batteries

111

Fig. 4.18 a Typical CV curves at a scan rate of 0.1 mV s-1 of the rGO/V2 O5 /PEO-MIL-53(Al)LiTFSI/Li battery at 80 °C. The 1st, 2nd, and 3rd scan intervals of the CV curves are of OCVs from 2.8 to 1.0 V, from 1.0 to 4.0 V, and from 1.0 to 4.0 V, respectively. b 1st, 2nd, 20th, and 40th charge/discharge profiles of the battery at a current rate of 17 mA g-1 at 80 °C. c Cycling performance of the all-solid-state lithium-vanadium battery: the capacity and efficiency versus cycle number at a current density of 17 mA g-1 at 80 °C. The inset shows the EIS results of the battery. d Photograph showing an LED light powered by the all-solid-state lithium-vanadium battery at 80 °C [176]. Reproduced with permission from Ref. [176]. Copyright ACS

up of atoms in a hexagonally close-packed network as shown in Fig. 4.19. This hexagonal structure allows for almost unrestricted expansion of the interlab distance upon intercalation of electron-donating species in the layer. Two types of coordination structures of the TMDs are possible, distinguished by unique sequencing of the three non-equivalent hexagonally close-packed positions designated as A, B, and C. Usually, either one or both the structures can form the basic unit of the crystal. The trigonal prismatic and octahedral coordination are described by the X-M-X sheets following the AbA and AbC sequences, respectively (Fig. 4.19). Capital letters in the sequence denote the chalcogen atoms, while the lower case letters represent the metal atoms [47]. Shi et al. [179] showed the eligibility of TMDs to be used as cathode active material solid-state batteries by employing 2D Co3 S4 hexagonal platelets coated on Li7 P3 S11 solid electrode for application in all-solid-state lithium batteries. The monodispersed 2D Co3 S4 hexagonal platelets were synthesized via precipitation and a series of topological reactions, and subsequently coated on Li7 P3 S11 electrolytes via an in situ liquid-phase reaction to form realized Co3 S4 @Li7 P3 S11 . An ASSLB employing the

112

M. S. Ratsoma et al.

Fig. 4.19 The octahedral and trigonal prismatic structures of MX 2 compounds. A, B, C represent the three non-equivalent positions for a close-packed stacking. In octahedron and tetrahedron, capital letters denote the chalcogen atoms and lower case letters the metal atoms [47]. Adapted from Ref. [47]. Copyright Springer

Co3 S4 @Li7 P3 S11 composite platelets as a cathode delivered a maximum reversible capacity of 685.9 mA h g-1 at a current density of 0.5 A g-1 after 50 cycles. Even at a high current density of 1 A g-1 , the Co3 S4 @Li7 P3 S11 composite cathode could still exhibit a high capacity of 457.3 mAh g-1 after 100 cycles. The structural and electrochemical characterization studies of the work are shown in Figs. 4.20 and 4.21. Wan et al. [180] demonstrated the enhancement of the electrochemical performance of the conversion reaction-based lithium storage pyrite (FeS2 ) cathode material by doping it with transition metals such as Ni, Co and Cu. Out of all the formed composite electrodes, the optimized Co0.1 Fe0.9 S2 electrode exhibited an excellent rate capability with capacities of 860.5, 797.7, 685.8 and 561.8 mAh g-1 being delivered after five cycles at current densities of 100, 200, 500 and 1000 mA g-1 , respectively. The improved rate capability is caused by the enhanced pseudocapacitive behaviours and improved reaction of Co0.1 Fe0.9 S2 compared to FeS2 electrode. An ASSLB assembled with the cathode active material showed an extraordinary cycling performance with a capacity of 543.5 mAh g-1 after 100 cycles at a current density of 500 mA g-1 .

4.4 Future Perspectives on All-Solid-State Battery Cathodes It has become patent from the reported literature that research focus on solid-state batteries has been largely at developing and advancing the electrolyte chemistry, and with batteries in general research efforts have been aimed at advancing the anode active material [38–42]. This trend has left rechargeable batteries with mostly exhausted cathode active material even though the electrochemical performance of the overall device largely depends on the cathode material. The little work done on

4 Prospective Cathode Materials for All-Solid-State Batteries

113

Fig. 4.20 a XRD patterns of β-Co(OH)2 , Co2+ -Co3+ LDHs, Co3 S4 platelets, Co3 S4 @Li7 P3 S11 composite platelets, and neat Li7P3S11 electrolytes. Scanning electron microscopy (SEM) images of b β-Co(OH)2 , c Co2+ -Co3+ LDHs, d Co3 S4 platelets, and e Co3 S4 @Li7 P3 S11 composite platelets. High-resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns of f, g Co3 S4 platelets and h, i Co3 S4 @Li7 P3 S11 composite platelets. j STEM-EDS elemental mapping images of Co3 S4 @Li7 P3 S11 composite platelets for Co, S, and P [179]. Reproduced with permission from Ref. [179]. Copyright ACS

cathode materials for rechargeable batteries mostly involves tweaking the same old materials, with no major change ever proposed for novel materials. Without doubting the well-documented and proven efficacy of the existing cathode materials in effecting practical electrochemical performances that have propelled sectors such as the portable electronic devices industry, many considerations have to be taken with regard to the eligibility of these materials going forward as the world transitions to green and clean energy. The transition has to be taken at a holistic approach, employing environmentally friendly materials in the energy storage and conversion systems considered to be vital for the transition. Therefore, more research

114

M. S. Ratsoma et al.

Fig. 4.21 A A Cyclic voltammograms of a Co3 S4 platelets and b Co3 S4 @Li7 P3 S11 composite platelets. Galvanostatic discharge–charge profiles of c Co3 S4 platelets and d Co3 S4 @Li7 P3 S11 composite platelets at a current density of 0.2 A g-1 . B a Discharge–charge profiles, b cycling performances, and c Nyquist plots after the 1st and 50th cycles of Co3 S4 platelets and Co3 S4 @Li7 P3 S11 composite platelets discharged and charged at 0.5 A g-1 . C Discharge–charge curves of the batteries using a Co3 S4 platelets and b Co3 S4 @Li7 P3 S11 composite platelets at various current densities. c Cycling stability at 1 A g-1 [179]. Reproduced with permission from Ref. [179]. Copyright ACS

efforts have to be afforded to the development of green electrode materials that will complement the transition. Substituting the non-flammable solid inorganic and polymeric electrolytes for the flammable liquid organic electrolytes in rechargeable batteries has improved the safety issues that have been encountered with these energy storage devices. The change also brings about a drastic change to the overall set-up of the battery pack, allowing for the fabrication of flexible microbatteries that would be suitable for application in small electronic devices and wearable technologies. However, the electrolyte phase change also brings about changes in the electrolyte–electrode dynamics, which impact the overall performance of the battery. Therefore, an advancement of the electrolyte with regard to safety and performance issues should be accompanied by an analogous development of electrode materials that will be complementary to the optimized operation of the electrolyte.

4 Prospective Cathode Materials for All-Solid-State Batteries

115

Overall, due to the wide electrochemical potential window offered by the SEs that lead to a great potential for developing high potential cathode materials with extremely high theoretical specific capacities [19–21], ASSBs emerge as the next generation energy storage devices that will meet the energy requirements of modern society by offering long cycle life, improved energy density and capacity, as well as improved safety. Future cathode materials for state-of-the-art all-solid-state batteries should be able to improve on the performance of the existing cathode active materials by offering improved cycling stability and overall electrode capacity with cost-effective raw material sourcing and electrode fabrication approaches.

4.5 Conclusion In this chapter we discussed the prospective cathode active material that can be applied in all-solid-state batteries (ASSBs), with a specific focus on all-solid-state lithium-ion batteries (ASSLIBs) and to a lesser extent the lithium metal batteries (ASSLBs). We looked at materials such as the lithiated transition metal compounds that are comprised of layered and spinel oxides (Lix M y Oz , M = Mn, Co, Ni, etc.), and the three-dimensional polyanionic compounds (Lix M y XOz , X = P, S, Si, Mo, W, etc.) and fluorinated polyanionic compounds (Lix M y XOz F). We have discussed in detail the structural aspects of such materials and the different preparation techniques/methods that have been used so far to synthesize materials of different sizes and morphologies. We also relayed how the latter mentioned aspects impact the electrochemical performance of the electrode material, giving examples of reported literature that employed the discussed cathode active materials in ASSLIBs and ASSLB. In addition to the many advantages of the said electrode materials discussed in this chapter, we also highlighted some of the drawbacks associated with such materials and how they have been demonstrated to be overcome in reported literature. In conclusion, we have detailed the requirements of ideal cathode active materials and also the extent the materials mentioned in this chapter reach in a bid to becoming the ideal cathode material. Acknowledgements MSR would like to thank the financial support from the Gauteng City Region Academy (GCRA). KM and KDM would like to thank the financial support from the National Research Foundation (NRF) (UID Nos. 138085, and 118113).

References 1. Lukatskaya, M.R., Dunn, B., Gogotsi, Y.: Multidimensional materials and device architectures for future hybrid energy storage. Nat. Commun. 7, 1–13 (2016) 2. Yang, Z., Zhang, J., Kintner-Meyer, M.C.W., Lu, X., Choi, D., Lemmon, J.P., Liu, J.: Electrochemical energy storage for green grid. Chem. Rev. 111, 3577–3613 (2011). https://doi.org/ 10.1021/cr100290v

116

M. S. Ratsoma et al.

3. Krishan, O., Suhag, S.: An updated review of energy storage systems: Classification and applications in distributed generation power systems incorporating renewable energy resources. Int. J. Energy Res. 43, 6171–6210 (2019). https://doi.org/10.1002/er.4285 4. Mauger, A., Julien, C.M., Paolella, A., Armand, M., Zaghib, K.: Building better batteries in the solid state: A review. Materials (Basel). 12, 1–86 (2019) 5. Oudenhoven, J.F.M., Baggetto, L., Notten, P.H.L.: All-solid-state lithium-ion microbatteries: A review of various three-dimensional concepts. Adv. Energy Mater. 1, 10–33 (2011). https:// doi.org/10.1002/aenm.201000002 6. Hess, S., Wohlfahrt-Mehrens, M., Wachtler, M.: Flammability of Li-Ion battery electrolytes: Flash point and self-extinguishing time measurements. J. Electrochem. Soc. 162, A3084– A3097 (2015). https://doi.org/10.1149/2.0121502jes 7. Simon, P., Gogotsi, Y., Dunn, B.: Where do batteries end and supercapacitors begin? Science 80(343), 1210–1211 (2014). https://doi.org/10.1126/science.1249625 8. Xu, B., Qian, D., Wang, Z., Meng, Y.S.: Recent progress in cathode materials research for advanced lithium ion batteries. Mater. Sci. Eng. R Rep. 73, 51–65 (2012). https://doi.org/10. 1016/j.mser.2012.05.003 9. Manthiram, A.: A reflection on lithium-ion battery cathode chemistry. Nat. Commun. 11, 1–9 (2020). https://doi.org/10.1038/s41467-020-15355-0 10. Günther, T., Billot, N., Schuster, J., Schnell, J., Spingler, F.B., Gasteiger, H.A.: The manufacturing of electrodes: Key process for the future success of Lithium-ion batteries. Adv. Mater. Res. 1140, 304–311 (2016). https://doi.org/10.4028/www.scientific.net/amr.1140.304 11. Hendricks, C., Williard, N., Mathew, S., Pecht, M.: A failure modes, mechanisms, and effects analysis (FMMEA) of lithium-ion batteries. J. Power Sources 297, 113–120 (2015). https:// doi.org/10.1016/j.jpowsour.2015.07.100 12. Knoche, T., Zinth, V., Schulz, M., Schnell, J., Gilles, R., Reinhart, G.: In situ visualization of the electrolyte solvent filling process by neutron radiography. J. Power Sources 331, 267–276 (2016). https://doi.org/10.1016/j.jpowsour.2016.09.037 13. Wood, D.L., Li, J., Daniel, C.: Prospects for reducing the processing cost of lithium ion batteries. J. Power Sources 275, 234–242 (2015). https://doi.org/10.1016/j.jpowsour.2014. 11.019 14. Simonetti, E., Carewska, M., Maresca, G., De Francesco, M., Appetecchi, G.B.: Highly conductive, ionic liquid-based polymer electrolytes. J. Electrochem. Soc. 164, A6213–A6219 (2017). https://doi.org/10.1149/2.0331701jes 15. Chen, J., Huang, X., Zhu, Y., Jiang, P.: Cellulose nanofiber supported 3D interconnected BN nanosheets for epoxy nanocomposites with ultrahigh thermal management capability. Adv. Funct. Mater. 27, 1–9 (2017). https://doi.org/10.1002/adfm.201604754 16. Takada, K.: Progress and prospective of solid-state lithium batteries. Acta Mater. 61, 759–770 (2013). https://doi.org/10.1016/j.actamat.2012.10.034 17. Hou, H., Xu, Q., Pang, Y., Li, L., Wang, J., Zhang, C., Sun, C.: Efficient storing energy harvested by triboelectric nanogenerators using a safe and durable all-solid-state sodium-ion battery. Adv. Sci. 4, 1–5 (2017). https://doi.org/10.1002/advs.201700072 18. Fergus, J.W.: Recent developments in cathode materials for lithium ion batteries. J. Power Sources 195, 939–954 (2010). https://doi.org/10.1016/j.jpowsour.2009.08.089 19. Chen, S., Xie, D., Liu, G., Mwizerwa, J.P., Zhang, Q., Zhao, Y., Xu, X., Yao, X.: Sulfide solid electrolytes for all-solid-state lithium batteries: Structure, conductivity, stability and application. Energy Storage Mater. 14, 58–74 (2018). https://doi.org/10.1016/j.ensm.2018. 02.020 20. Sun, C., Liu, J., Gong, Y., Wilkinson, D.P., Zhang, J.: Recent advances in all-solid-state rechargeable lithium batteries. Nano Energy 33, 363–386 (2017). https://doi.org/10.1016/j. nanoen.2017.01.028 21. Kamaya, N., Homma, K., Yamakawa, Y., Hirayama, M., Kanno, R., Yonemura, M., Kamiyama, T., Kato, Y., Hama, S., Kawamoto, K., Mitsui, A.: A lithium superionic conductor. Nat Mater 10, 682–686 (2011). https://doi.org/10.1038/nmat3066

4 Prospective Cathode Materials for All-Solid-State Batteries

117

22. Luntz, A.C., Voss, J., Reuter, K.: Interfacial challenges in solid-state Li Ion batteries. J. Phys. Chem. Lett. 6, 4599–4604 (2015). https://doi.org/10.1021/acs.jpclett.5b02352 23. Wu, B., Wang, S., Evans, W.J., Deng, D.Z., Yang, J., Xiao, J.: Interfacial behaviours between lithium ion conductors and electrode materials in various battery systems. J. Mater. Chem. A 4, 15266–15280 (2016). https://doi.org/10.1039/c6ta05439k 24. Han, X., Gong, Y., Fu, K., He, X., Hitz, G.T., Dai, J., Pearse, A., Liu, B., Wang, H., Rubloff, G., Mo, Y., Thangadurai, V., Wachsman, E.D., Hu, L.: Negating interfacial impedance in garnet-based solid-state Li metal batteries. Nat Mater. 16, 572–579 (2017). https://doi.org/10. 1038/nmat4821 25. Kim, Y.J., Rajagopal, R., Kang, S., Ryu, K.S.: Novel dry deposition of LiNbO3 or Li2ZrO3 on LiNi0.6Co0.2Mn0.2O2 for high performance all-solid-state lithium batteries. Chem. Eng. J. 386 (2020). https://doi.org/10.1016/j.cej.2019.123975 26. Zhang, W., Richter, F.H., Culver, S.P., Leichtweiss, T., Lozano, J.G., Dietrich, C., Bruce, P.G., Zeier, W.G., Janek, J.: Degradation mechanisms at the Li10GeP2S12/LiCoO2 cathode interface in an all-solid-state Lithium-ion battery. ACS Appl. Mater. Interfaces 10, 22226– 22236 (2018). https://doi.org/10.1021/acsami.8b05132 27. Schnell, J., Günther, T., Knoche, T., Vieider, C., Köhler, L., Just, A., Keller, M., Passerini, S., Reinhart, G.: All-solid-state lithium-ion and lithium metal batteries–paving the way to large-scale production. J. Power Sources 382, 160–175 (2018). https://doi.org/10.1016/j.jpo wsour.2018.02.062 28. Sakuda, A., Hayashi, A., Tatsumisago, M.: Sulfide solid electrolyte with favorable mechanical property for all-solid-state lithium battery. Sci. Rep. 3, 2–6 (2013). https://doi.org/10.1038/ srep02261 29. Yue, L., Ma, J., Zhang, J., Zhao, J., Dong, S., Liu, Z., Cui, G., Chen, L.: All solid-state polymer electrolytes for high-performance lithium ion batteries. Energy Storage Mater. 5, 139–164 (2016). https://doi.org/10.1016/j.ensm.2016.07.003 30. Zhu, Y., He, X., Mo, Y.: Origin of outstanding stability in the lithium solid electrolyte materials: Insights from thermodynamic analyses based on first-principles calculations. ACS Appl. Mater. Interfaces 7, 23685–23693 (2015). https://doi.org/10.1021/acsami.5b07517 31. Xie, J., Imanishi, N., Zhang, T., Hirano, A., Takeda, Y., Yamamoto, O.: Li-ion transport in allsolid-state lithium batteries with LiCoO2 using NASICON-type glass ceramic electrolytes. J Power Sources 189, 365–370 (2009). https://doi.org/10.1016/j.jpowsour.2008.08.015 32. Ren, Y., Chen, K., Chen, R., Liu, T., Zhang, Y., Nan, C.W.: Oxide electrolytes for lithium batteries. J. Am. Ceram. Soc. 98, 3603–3623 (2015). https://doi.org/10.1111/jace.13844 33. Sakuda, A., Hayashi, A., Tatsumisago, M.: Interfacial observation between LiCoO2 electrode and Li 2S–P2S5 solid electrolytes of all-solid-state lithium secondary batteries using transmission electron microscopy. Chem Mater 22, 949–956 (2010). https://doi.org/10.1021/cm9 01819c 34. Ohta, N., Takada, K., Zhang, L., Ma, R., Osada, M., Sasaki, T.: Enhancement of the high-rate capability of solid-state lithium batteries by nanoscale interfacial modification. Adv. Mater. 18, 2226–2229 (2006). https://doi.org/10.1002/adma.200502604 35. MacHida, N., Kashiwagi, J., Naito, M., Shigematsu, T.: Electrochemical properties of allsolid-state batteries with ZrO 2-coated LiNi 1/3Mn 1/3Co 1/3O 2 as cathode materials. Solid State Ion. 225, 354–358 (2012). https://doi.org/10.1016/j.ssi.2011.11.026 36. Ohta, S., Seki, J., Yagi, Y., Kihira, Y., Tani, T., Asaoka, T.: Co-sinterable lithium garnet-type oxide electrolyte with cathode for all-solid-state lithium ion battery. J. Power Sources 265, 40–44 (2014). https://doi.org/10.1016/j.jpowsour.2014.04.065 37. Kato, T., Yoshida, R., Yamamoto, K., Hirayama, T., Motoyama, M., West, W.C., Iriyama, Y.: Effects of sintering temperature on interfacial structure and interfacial resistance for all-solidstate rechargeable lithium batteries. J. Power Sources 325, 584–590 (2016). https://doi.org/ 10.1016/j.jpowsour.2016.06.068 38. Li, X., Sun, Q., Wang, Z., Song, D., Zhang, H., Shi, X., Li, C., Zhang, L., Zhu, L.: Outstanding electrochemical performances of the all-solid-state lithium battery using Ni-rich layered oxide cathode and sulfide electrolyte. J. Power Sources 456, 227997 (2020). https://doi.org/10.1016/ j.jpowsour.2020.227997

118

M. S. Ratsoma et al.

39. Tan, D.H.S., Banerjee, A., Chen, Z., Meng, Y.S.: From nanoscale interface characterization to sustainable energy storage using all-solid-state batteries. Nat. Nanotechnol. 15, 170–180 (2020). https://doi.org/10.1038/s41565-020-0657-x 40. Jung, W.D., Kim, J.S., Choi, S., Kim, S., Jeon, M., Jung, H.G., Chung, K.Y., Lee, J.H., Kim, B.K., Lee, J.H., Kim, H.: Superionic halogen-rich Li-argyrodites using in situ nanocrystal nucleation and rapid crystal growth. ACS Appl. Mater. Interfaces (2020). https://doi.org/10. 1021/acs.nanolett.9b04597 41. Liang, J., Chen, N., Li, X., Li, X., Adair, K.R., Li, J., Wang, C., Yu, C., Norouzi Banis, M., Zhang, L., Zhao, S., Lu, S., Huang, H., Li, R., Huang, Y., Sun, X.: Li10Ge(P1-xSb x)2S12 lithium-ion conductors with enhanced atmospheric stability. Chem. Mater. 32, 2664–2672 (2020). https://doi.org/10.1021/acs.chemmater.9b04764 42. Jung, S.H., Kim, U.H., Kim, J.H., Jun, S., Yoon, C.S., Jung, Y.S., Sun, Y.K.: Ni-Rich Layered cathode materials with electrochemo-mechanically compliant microstructures for all-solidstate Li batteries. Adv. Energy Mater. 10, 1–12 (2020). https://doi.org/10.1002/aenm.201 903360 43. Manthiram, A., Yu, X., Wang, S.: Lithium battery chemistries enabled by solid-state electrolytes. Nat. Rev. Mater. 2, 1–16 (2017). https://doi.org/10.1038/natrevmats.2016.103 44. Nitta, N., Wu, F., Lee, J.T., Yushin, G.: Li-ion battery materials: Present and future. Mater. Today 18, 252–264 (2015) 45. Bensalah, N., Dawood, H.: Review on synthesis, characterizations, and electrochemical properties of cathode materials for Lithium ion batteries. J. Mater. Sci. Eng. 5(2016). https://doi. org/10.4172/2169-0022.1000258 46. Whittingham, M.S.: Lithium batteries and cathode materials. Chem. Rev. 104, 4271–4301 (2004). https://doi.org/10.1021/cr020731c 47. Julien, C., Mauger, A., Vijh, A., Zaghib, K.: Lithium Batteries: Science and Technology. Springer International Publishing, Cham (2015) 48. Rouxel, J.: Alkali Metal Intercalation Compounds of Transition Metal Chalcogenides: TX2, TX3 and TX4 Chalcogenides. In: Levy, F. (ed.) Intercalated Layered Materials, pp. 201–250. Springer, Netherlands, Dordrecht (1979) 49. Whittingham, M.S.: Chemistry of intercalation compounds: Metal guests in chalcogenide hosts. Prog. Solid State Chem. 12, 41–99 (1978). https://doi.org/10.1016/0079-6786(78)900 03-1 50. Friend, R.H., Yoffe, A.D.: Electronic properties of intercalation complexes of the transition metal dichalcogenides. Adv. Phys. 36, 1–94 (1987). https://doi.org/10.1080/000187387001 01951 51. Dresselhaus, M.S., Dresselhaus, G.: Intercalation compounds of graphite. Adv. Phys. 30, 139–326 (1981). https://doi.org/10.1080/00018738100101367 52. Whittingham, M.: Intercalation chemistry: an introduction. In: Whittingham, M., Jacobson, A. (eds.) Intercalation Chemistry, pp. 1–18. Academic, New York (1982) 53. Julien, C., Nazri, G.A.: Intercalation compounds for advanced lithium batteries. In: Nalwa, H. (ed.) Handbook of Advanced Electronic and Photonic Materials and Devices, pp. 99–184. Elsevier, San Diego, CA (2001) 54. Julien, C.M.: Lithium intercalated compounds: Charge transfer and related properties. Mater. Sci. Eng. R Rep. 40, 47–102 (2003). https://doi.org/10.1016/S0927-796X(02)00104-3 55. Mizushima, K., Jones, P., Wiseman, P., Goodenough, J.: LixCoO2 (090%), restoration of materials in their highly pure form, versatility in handling different cathode chemistries, the minimum exhaust of toxic gases, and low cost [64]. Before the acid leaching step, the current collectors and cell wrapping materials are removed by mechanical separation and sieving, in order to hasten the reaction rate.

9 Recycling of All-Solid-State Lithium-Ion Batteries

263

The next step is to heat and remove the remaining organic components, which are then dispersed in solutions of hydrogen peroxide or sulphuric acid. In doing so, the cathode materials get dissolved, and the carbon-based materials remain undissolved, which can be collected for further regeneration. But this cannot be counted as a pyrometallurgical process. Hydrometallurgy is extremely useful in the recycling of solid-state electrolyte materials as well as LiNix Mny Coz O2 (NMC) cathode with a high level of purity, through the co-precipitation of these materials by optimizing the pH [65]. Hydrometallurgy is highly effective in terms of high purity of recycling, high recovery rate, and low CO2 emissions. However the process can be counted as expensive when considering input cost of materials to be used in the process. Further, a large amount of dangerous waste solutions are generated, and may not be suitable for all ASSB systems. Pretreatment of Li metal should be done properly for its usage in hydrometallurgy, as it can trigger violent reactions with the solution used for leaching. Sulfide-based solid electrolyte produces H2 S gas during hydrometallurgy. Another issue lies with the recycling of polymer-based electrolytes is the increase in the viscosity of the solution used for hydrometallurgy, which can adversely affect the co-precipitation of the components to be recycled [66]. For oxide-based solid-state electrolytes and transition metal oxide-based cathodes, selection of counter anions for their precipitation should be done carefully, to maintain their identical chemistry. Sulfate solution mixed with certain extractants such as Na-D2EPHA and Na-Cyanex272 has been proved to be effective in the efficacious separation of manganese, cobalt, and nickel, with the careful adjustment of pH and temperature [67]. From this particular accomplishment, it follows that optimization of reactor parameters and the use of suitable solvents such as Cyanex-572 may be quite useful for the selective filtering of rare earth elements from solid-state electrolytes and metal oxide-based cathodes. Further, there exists a major difference in Ksp values of metal hydroxides of zirconium, titanium, and lanthanum (prominent constituents oxide-based solid-state electrolytes), and metals such as cobalt, manganese, and nickel (major components of oxide-based cathodes) [68, 69]. This difference in Ksp values can be exploited for selective sedimentation of solid-state electrolytes from cathode materials, provided that the support of extractant and chelating agents would be required for obtaining desirable morphologies. As a whole, hydrometallurgy is outstanding for the recycling of conventional anodes and cathodes. But the complex chemistries of solid-state electrolytes and the combination of cathode and solid electrolytes make it difficult to be applied for the recycling of ASSBs. The various techniques involved in the hydrometallurgical process are Leaching: Through this process, the metals present in used batteries are dissolved in suitable solvents, and later the dissolved ions can be separated to obtain final products. Alkali Leaching: It’s a selective leaching technique that can avoid costly postprocessings such as separation and purification. Ammonia-based systems are used to dissolve the metal ions such as Ni, Co, and Cu, owing to the capability of ammonia to form complex with these metals. A suitable combination is to use ammonia/ammonium sulfate as the solution for leaching and to use sulfites as the

264

K. Ajith et al.

reducing agents for the recovery of metals. While using ammonia(NH3 )/ammonium sulfate ((NH4 )2 SO4 ) as a leaching solution in combination with sodium sulfite (Na2 SO3 ) as the reducing agent, the leaching efficiencies for Ni, Co, Mn and Li are found to be 94.8%, 88.4%, 6.34%, and 96.7%, respectively [70]. Acid Leaching: Acid leaching has high recovery efficiency. While using inorganic acids for leaching, it may lead to the evolution of toxic gases, and hence can be a cause of pollution. To overcome this, organic acids can be used as leaching agents. Typical candidates used for acid leaching are HNO3 , H2 SO4 , HCl, citric acid, oxalic acid, formic acid, and ascorbic acid. It has been demonstrated that the use of dense HCl and H2 SO4 —H2 O2 systems can attain a leaching efficiency of 99% for the dissolution of Co, Mn, and Li metals [71]. In one of the research work, it was shown that it is possible to recover LiFePO4 by using a dilute leaching solution of sulfuric acid and hydrogen peroxide [72]. Here the amount of acid used was quite low, and it was also demonstrated that the waste generated by the use of low amount of inorganic acid can be very low. In the case of organic acids, it was demonstrated that the use of formic acid can be used for the leaching of Li ions into the solution by the selective precipitation of other metal ions [73]. In another approach to recycling NMC cathode, oxalic acid was used to dissolve lithium, while Co, Mn, and Ni were precipitated as corresponding oxalates [74].

9.6.4 Direct Recycling In simple terms, direct recycling just means the use of no chemistry in the process of recycling. The method is highly economical than conventional recycling as there is significantly lower energy expenditure needed. In fact, the energy stored in NMC cathodes and solid-state electrolytes are drawn out for recycling. A better comparison of energy expenditure in direct recycling, hydrometallurgy, and pyrometallurgy has been provided in a study that uses the Everbatt model for LiCoO2 . [75]. It follows from this study that the required energy for the processing of solid electrolytes is ≈5 MJ/kg, and that of the cathode is ≈0.6 kgCO2eq , respectively. To compare, the corresponding energy in the cases of hydrometallurgy and pyrometallurgy are ≈31 and ≈19 MJ/kg for the cathode, ≈2.3 MJ/kg, and ≈2.5 kgCO2eq , respectively. From this, it is quite obvious that the direct recycling can make the recycling of ASSBs highly economical. Laboratory-level studies on direct recycling prove that different types of direct recycling methods can be applied to common cathode chemistries. In direct recycling, the lithium-depleted cathode material is made to react with a lithium source to retrieve its original stoichiometry. In addition, heat treatment can be done to regain the morphology and surface structure [76].

9 Recycling of All-Solid-State Lithium-Ion Batteries

265

9.6.5 Hydrothermal Regeneration In this process, depleted cathode materials are made to react with aqueous solution of lithium salts, inside an autoclave reactor between 100 and 200 °C for a few hours. Then the products are washed, filtered, and subjected to a mild heat treatment to retrieve surface properties [77, 78]. Hydrothermal regeneration has a greater advantage over conventional solid-state recycling, since the former can ensure the recycling of cathode materials at various levels of lithium depletion. While in solid-state regeneration processes, we may require batch to batch analysis of chemical composition in order to decide the quantity of lithium salts required [79]. Even though solid-state electrolytes such as LATP (Li1+x Alx Ti2−x (PO4 )3 ) can be synthesized through hydrothermal methods, the regeneration of the same through the hydrothermal method is quite limited, as there are the limited number of studies exist on the same. But it can be reasonably speculated that the regeneration of oxidebased solid-state electrolytes through hydrothermal method can be possible due to the similarity in the chemical composition of the same with oxide-based cathode materials [80].

9.6.6 Dissolution/Precipitation This approach is particularly suited for sulfide-based solid electrolytes, owing to their solubility in polar solvents due to the presence of PS4 3− thiophosphate radical [81]. One of the plus points of the method is that the solvents used are cheap and safe. Sulfide-based solid electrolytes can be readily dissolved in acetonitrile or ethanol and can be easily filtered out from the rest of the components. The solvents used do not react with anode or cathode materials. Further, the dissolution occurs without the chemical breakage of the sulfide-based solid electrolytes. Hence the electrolyte can be dissolved and recrystallized, for its reuse in future ASSBs [82]. The components which remain insoluble (anode and cathode materials), can be retrieved separately. Following the recovery of precipitated sulfide-based solid electrolytes from polar solvents, a mild heat treatment is performed on the former to increase the grain size to improve conductivity. This is followed by the preparation of dense electrolyte films. The process of dissolution and precipitation requires low energy and produces low amount of residual waste. But the yield is quite higher when compared with similar processes. Besides sulfide-based solid electrolytes, a few polymer-based solid electrolytes can also be recycled and recovered using dissolution/precipitation methods. A typical example is the separation of PEO-based solid-state electrolytes from the battery black mass, owing to the easy solubility of PEO in a few polar solvents in water. The solubility of widely used lithium salts such as LiTFSI can be exploited in the cost-effective and safe recycling of polymer-based solid-state electrolytes. It has

266

K. Ajith et al.

been demonstrated that monomers of PEO can readily be dissolved in water without the need of any stirring/agitation [83]. This is followed by the evaporation of water to recover the Li salts and monomers.

9.7 State-of-the-Art Research in ASSLIB Recycling Till date, there are no recognized commercial techniques for the recycling of ASSLIBs, but there exist methods for conventional LIBs. However, there is the availability of a limited amount of research in conventional LIB recycling with an outlook at modifying the techniques toward the recycling of ASSLIBs. As an example, in the work of Wang et al., the authors propose a benign hydrometallurgical method using phytic acid as the precipitant for the recovery of Mn ions from spent LiMn2 O4 batteries [84]. The authors claim that this method can also be applied to other commercial batteries. Further, they insist that the regenerated materials through this technique can be well suited for the application in ASSLIBs. They support this claim in terms of the electrochemical stability of the interface of a solid-state battery constructed with synthetic PL-Mn2 P5 solid electrolyte and commercial LiFePO4 cathode.

9.8 Outlook for ASSLIB Recycling Azhari et al. [1] had proposed a possible design for recycling of ASSLIBs. The process flow involves several steps as shown in Fig. 9.12. The first step involves the separation of cell packs based on internal chemistry. This is then examined for the state of health followed by discharging completely to recover the stored electrical energy if any and to minimize the quantity of reactive components including residual lithium. In case the aforesaid is not possible, the cell pack should be disassembled in an argon-filled glove box in a CO2 atmosphere, followed by shredding and crushing. This method has been previously demonstrated for conventional LIBs, and it reduces the risk of workers in the hazardous environment, prevents the cell components being reacting with moisture, prevention of H2 S formation if any sulfide SSE is involved, and the conversion of residual lithium to lithium carbonate owing to the presence of CO2 [80]. The whole process is then followed by sieving of the materials to separate the outer cell pack and current collectors. The obtained anode, cathode, and SSE powders are then dispersed and washed using any polar solvent such as ethanol, to dissolve sulfide SSEs. The solution is then filtered to remove the insoluble components. The sulfide SSEs can be recrystallized by evaporating the solution. For the separation of PEO-based polymer SSEs, the mixture is additionally washed using a water/alcohol mixture above 50 °C [85]. The resulting solution was heated to remove the solvents to obtain the SSEs. The residual components can be subjected to hydrometallurgical and hydrothermal techniques.

9 Recycling of All-Solid-State Lithium-Ion Batteries

267

Fig. 9.12 Simplified flow sheet of the Umicore Battery Recycling Process. Reprinted from Ref. [63]. Copyright 2015 MDPI

In the hydrothermal process separation of graphite or carbon black is suggested first, using gravimetric separation. This can be followed by dispersion of cathodeSSE mixture into an aqueous solution. The lithium carbonate present as a result of any previous reaction (such as interfacial reactions) could contribute to the aqueous solution needed for hydrothermal regeneration. Following the process, the obtained powders can be measured for chemical composition, with the addition of an extra amount of SSE or cathode powders for the targeted electrode/electrolyte ratio. This is then followed by co-sintering to improve the surface morphology and to create cathode/SSE particle contacts, ahead of a new ASSLIB assembly. For battery scrap volumes that contain cathodes or oxide-based SSEs of varying chemistry, hydrometallurgy is the most suitable technique. Solid mass can be subjected to acid leaching, provided that inert carbon black and graphite are separated as filter cakes. To obtain the NMC cathode and SSEs, ICP analysis and additional transition metal salts would be needed. The process of acid leaching is then followed by the addition of chelating agents, selective counter anions, and extractants to precipitate the precursors of NMC cathode. Afterward, the SSE precursors can be precipitated. NMC materials and SSE materials are then suggested for lithiation and solid-state heat treatment for reuse in ASSLIBS (Fig. 9.13).

268

K. Ajith et al.

Fig. 9.13 Flow chart for an idealized recycling system utilizing Hydrometallurgy and direct recycling methods. Reprinted from Ref. [1]. Copyright 2020 CellPress

9 Recycling of All-Solid-State Lithium-Ion Batteries

269

9.9 Reuse and Re-purposing of Recycled Materials The freakiest form of ASSLIBs is the electric vehicle batteries, which are the most demanding power choice for the ongoing/upcoming revolution in the transport sector. However, it is a matter of fact that, once the battery capacity is inadequate to power up the motor/engine of the vehicle, the battery is removed for recycling [86]. Still, the battery bears sufficient storage capacities so that it can be used for non-vehicular necessities. Hence the terms ‘reuse’ as well as ‘re-purposing’ of batteries/battery materials are equally important as recycling, from the environmental perspective. To explain the term ‘reuse’, simply consider the installation of a used EV battery (of a larger vehicle such as a bus or truck) for another vehicle (such as a low cc bike or scooter). ‘Repurpose’ is different in such a manner that the used EV battery may be used for small-scale grid storage or home UPS applications. Recycling of EV batteries is not quite economical since they can retain around 80% of their initially manufactured capacity. Before re-purposing, the state-of-health (SOH) and energy storage capacity of the battery has to be checked, and this would require battery testing infrastructure. The residual energy storage capacity of the battery is dependent on its initial use and capacity. Till now, there are no standardized methods to classify the re-purposed batteries. The only way to filter out batteries that can be re-purposed is to analyze the SOH. There are various constraints that determine the degradation of battery packs, leading to different SOH. The type of the vehicle, nature of driving, and the location/area where the vehicle was driven determine the SOH of the battery used in it. The capacity of the battery decreases as it ages. Besides the age-related battery degradation, there is another type of degradation that results from the operation of the battery [87]. Hence the combined effect of these two types of degradations results in a decrease in SOH. Various other factors such as mechanical stress and temperature can also affect the overall health of the battery. In research, a five-level system (a classification is given in Table 9.1) has been proposed for analyzing the SOH of the EV batteries [87]. Since the batteries that occupy first and second level has ≥80% capacity remaining, they can be used for lower grade electric vehicles again. Batteries that belong to level 3 have sufficient storage for a re-purposed application. Batteries that own levels four and five are the ones that are significantly degraded or catastrophically damaged. They can’t be subjected to reuse or re-purposing, the only way is to recycle the materials. There exists a number of hurdles to be surpassed for the re-purposing of ASSLIBs for stationary applications. Insurance premium is quite higher due to the higher cost of re-purposed batteries. Besides insurance, the ownership of the battery is another barrier to the re-purposing of batteries. In situations where the battery gets damaged due to fire or leak, the liability of the same has to be owned by someone.

270

K. Ajith et al.

Table 9.1 Re-purposed battery pack classification Level

Description

Level 1

Little or no degradation (≥80% capacity remaining) [86]

Level 2

Some degradation, vehicle reuse (≥80% capacity remaining) [86]

Level 3

Some degradation, stationary re-purposing

Level 4

Significant degradation, material recycling

Level 5

Catastrophic failure/damage, material recycling

Coming to the reuse of materials in the battery, there are research reports on the reuse of anode scrap of spent LIBs in the high-performance cathodes in the electroFenton system. Different recovery processes such as anode raw powder (RP), acid leaching (AL), acide-alkali leaching (AAL) residual powder were employed and it was confirmed that these processes change the functional groups of the anode powder. This can significantly affect their reuse in the electron-Fenton system [88].

9.10 Summary and Conclusion Compared to other chapters, this chapter has a different type of significance from the ethical perspective, as it deals with the recycling of ASSLIBs. Apart from the technological and commercial aspects, the process of recycling and reuse of battery material can be viewed as a valuable service offered to the coming generations, since the preservation and maintenance of natural resources in their pure form are essential for the survival of life on earth. The initial sections of the chapter deal with the failure mechanisms of both LIBs and ASSLIBs, with more focus on the failure of ASSLIBs. Understanding the battery failure and its aftermath are of high significance in formulating the most suitable techniques for each and every type of cathodes and SSEs in the battery. It has been understood that the failure of ASSLIBs is highly dependent on the electrode/electrolyte interfaces. Formation of space charge layer, interdiffusion of elements interfacial reactions of SSE with cathode active material and conductive additives, and electro-chemomechanical failure are the major causes of the failure of cathode/SSE interfaces. Lithium Dendrite formation and SSE/Li interfacial reactions are the main reasons for the failure of SSE/Li metal interface. The importance of failure mechanisms for battery recycling is in the sense that, the used-up battery may contain various types of new chemical phases different from those present at the time of manufacturing. The identification of such byproducts helps in the correct framing of recycling techniques for a particular ASSLIB type. The chapter then provides an overview of the general techniques used in battery recycling, followed by the discussion of cell engineering (construction) and recycling strategies for ASSLIBs. Mechanical separation, pyrometallurgy, Hydrometallurgical techniques involving various types of leaching, direct recycling, hydrothermal regeneration, and dissolution/precipitation are the methods of recycling for ASSLIBs under

9 Recycling of All-Solid-State Lithium-Ion Batteries

271

research. It shall be noted that there are no acclaimed methods of recycling specifically for ASSLIBs at the commercial level. It is expected that the recycling research will be specifically directed to ASSLIBs once the same gets commercialized. The proposed techniques under present-day research are just extensions of conventional LIB recycling methods. However, a few studies provide viewpoints for developing effective recycling techniques for ASSLIBs. To conclude, it can be said that the recycling of ASSLIBs is an unexplored area, and much amount of research has to be done on the same. Further, the major challenges with All-Solid-State battery recycling are speculated to be economic and legal support by governments, availability of spent batteries and output materials, economic feasibility, and safety of recycling technologies (especially for the recovery of Li metal from ASSLIB scrap volume). Acknowledgements The authors (K. Ajith, P. C. Selvin, P. Adlin Helen, and G. Somasundharam) are highly grateful toward Dr. Nithyadharseni Palaniyandy, Council for Scientific and Industrial Research (CSIR), South Africa, and Dr. K. P. Abhilash, University of Chemistry and Technology, Prague, the Czech Republic for providing the opportunity to write this chapter, and for their constant monitoring and motivation. K. P. A. was supported by the European Structural and Investment Funds, OP RDE funded project ‘CHEMFELLS IV’ (No. CZ.02.2.69/0.0/0.0/20_079/0017899).

References 1. Azhari, L., Bong, S., Ma, X., Wang, Y.: Matter 3, 1845–1861 (2020) 2. Chen, M., Ma, X., Chen, B., Arsenault, R., Karlson, P., Simon, N., Wang, Y.: Joule 3, 2622–2646 (2019) 3. Fan, E., Li, L., Wang, Z., Lin, J., Huang, Y., Yao, Y., Chen, R., Wu, F.: Chem. Rev. 120, 7020–7063 (2020) 4. Takada, K., Ohta, N., Zhang, L., Fukuda, K., Sakaguchi, I., Ma, R., Osada, M., Sasaki, T.: Solid State Ions. 179, 1333–1337 (2008) 5. Luntz, A.C., Voss, J., Reuter, K.: J. Phys. Chem. Lett. 6, 4599–4604 (2015) 6. Pan, Q., Barbash, D., Smith, D.M., Qi, H., Gleeson, S.E., Li, C.Y.: Adv. Energy Mater. 7(22), 1701231 (2017) 7. Hartmann, P., Leichtweiss, T., Busche, M.R., Schneider, M., Reich, M., Sann, J., Adelhelm, P., Janek, J.: J. Phys. Chem. C 117, 21064–21074 (2013) 8. Ohta, N., Takada, K., Zhang, L., Ma, R., Osada, M., Sasaki, T.: Adv. Mater. 18, 2226–2229 (2006) 9. JieLian, P., Zhao, B.-S., Zhang, L.-Q., Xu, N., Wu, M.-T., Gao, X.-P.: J. Mater. Chem. A 7, 20540–20557 (2019) 10. Mizuno, F., Yada, C., Iba, H.: Lithium-ion Batteries. Advances and Applications, pp. 273–291 (2014) 11. Kim, K.H., Iriyama, Y., Yamamoto, K., Kumazaki, K., Asaka, T., Tanabe, K., Fisher, C.A.J., Hirayama, T., Murugan, R., Ogumi, Z.: J. power sources 196, 764–767 (2011) 12. Ma, J., Chen, B., Wang, L., Cui, G.: J. Power Sources 392, 94–115 (2018) 13. Auvergniot, J., Cassel, A., Ledeuil, J.-B., Viallet, V., Seznec, V., Dedryvère, R.: Chem. Mater. 29(9), 3883–3890 (2017)

272

K. Ajith et al.

14. 15. 16. 17. 18. 19. 20. 21.

Sumita, M., Tanaka, Y., Ikeda, M., Ohno, T.: J. Phys. Chem. C 120, 13332–13339 (2016) Richards, W.D., Miara, L.J., Wang, Y., Kim, J.C., Ceder, G.: Chem. Mater. 28, 266–273 (2016) Hansel, C., Afyon, S., Rupp, J.L.: Chem. Mater. 8, 18412–18420 (2016) Chung, H., Kang, B.: Chem. Mater. 29, 8611–8619 (2017) Mizuno, F., Hayashi, A., Tadanaga, K., Tatsumisago, M.: J. Power Sources 146, 711–714 (2005) Han, F., Zhu, Y., He, X., Mo, Y., Wang, C.: Adv. Energy Mater. 6, 1501590 (2016) Oh, G., Hirayama, M., Kwon, O., Suzuki, K., Kanno, R.: Chem. Mater. 28, 2634–2640 (2016) Zhang, W., Leichtweiss, T., Culver, S.P., Koerver, R., Das, D., Weber, D.A., Zeier, W.G., Janek, J.: ACS Appl. Mater. Interfaces 9, 35888–35896 (2017) Dollé, M., Sannier, L., Beaudoin, B., Trentin, M., Tarascon, J.M.: Electrochem. Solid State Lett. 5, A286–A289 (2002) Monroe, C., Newman, J.: J. Electrochem. Soc. 151, A880 (2004) Monroe, C., Newman, J.: J. Electrochem. Soc. 152, A396–A404 (2005) Ni, J.E., Case, E.D., Sakamoto, J.S., Rangasamy, E., Wolfenstine, J.B.: J. Mater. Sci. 47, 7978–7985 (2012) Tsai, C.L., Roddatis, V., Chandran, C.V., Ma, Q., Uhlenbruck, S., Bram, M., Heitjans, P., Guillon, O.: ACS Appl. Mater. Interfaces 8, 10617–10626 (2016) Ishiguro, K., Nakata, Y., Matsui, M., Uechi, I., Takeda, Y., Yamamoto, O., Imanishi, N.: J. Electrochem. Soc. 160, A1690–A1693 (2013) Suzuki, Y., Kami, K., Watanabe, K., Watanabe, A., Saito, N., Ohnishi, T., Takada, K., Sudo, R., Imanishi, N.: Transparent cubic garnet-type solid electrolyte of Al2 O3 -doped Li7 La3 Zr2 O12 . Solid State Ion. 278, 172–176 (2015) Tsai, C.L., Roddatis, V., Chandran, C.V., Ma, Q., Uhlenbluck, U., Martin, B., Heitjans, P., Olivier, G., Cheng, L., Chen, W., Kunz, M., Persson, K., Tamura, N., Chen, G., Doeff, M.: ACS Appl. Mater. Interfaces 7(3), 2073–2081 (2015) Kotobuki, M., Munakata, H., Kanamura, K., Sato, Y., Yoshida, T.: J. Electrochem. Soc. 157, A1076–A1079 (2010) Whiteley, J.M., Woo, J.H., Hu, E., Nam, K.W., Lee, S.H.: J. Electrochem. Soc. 161, A1812– A1817 (2014) Wenzel, S., Randau, S., Leichtwei, T., Weber, D.A., Sann, J., Zeier, W.G.: J. Janek. Chem. Mater. 28, 2400–2407 (2016) Cheng, T., Merinov, B.V., Morozov, S., Goddard, W.A.: ACS Energy Lett. 2, 1454–1459 (2017) Wenzel, S., Leichtweiss, T., Krüger, D., Sann, J., Janek, J.: Solid State Ion. 278, 98–105 (2015). https://doi.org/10.1016/j.ssi.2015.06.001 Wang, C., Gong, Y., Liu, B., Fu, K., Yao, Y., Hitz, E., Li, Y., Dai, J., Xu, S., Luo, W., Wachsman, E.D., Hu, L.: Nano Lett. 17, 565–571 (2017) Du, F., Zhao, N., Li, Y., Chen, C., Liu, Z., Guo, X.: J. Power Sources 300, 24–28 (2015) Luo, W., Gong, Y., Zhu, Y., Fu, K.K., Dai, J., Lacey, S.D., Wang, C., Liu, B., Han, X., Mo, Y., Wachsman, E.D., Hu, L.: J. Am. Chem. Soc. 138, 12258–12262 (2016) Harper, G., Sommerville, R., Kendrick, E., Driscoll, L., Slater, P., Stolkin, R., Walton, A., Christensen, P., Heidrich, O., Lambert, S., Abbott, A., Ryder, K., Gaines, L., Anderson, P.: Nature 575, 75–86 (2019) Zheng, X., Zhu, Z., Lin, X., Zhang, Y., He, Y., Cao, H., Sun, Z.: Engineering 4(3), 361–370 (2018) Trager, T., Friedrich, B., Weyhe, R.: Chem. Ing. Tech. 87, 1550–1557 (2015) Diaz, F., Wang, Y., Moorthy, T.: B. Friedrich. 8, 565 (2018) Wang, H., Vest, M., Friedrich, B.: Metals 10, 1523 (2020) Sun, L., Qiu, K.: Materials 194, 378–384 (2011) Hanisch, C., Loellhoe, T., Diekmann, J., Markley, K., Haselrieder, W., Kwade, A.: J. Clean. Prod. 108, 301–311 (2015) Pagliaro, M., Meneguzzo, F.: Heliyon 5, e01866 (2019) Chen, Y., Liu, N., Jie, Y., Hu, F., Li, Y., Wilson, B.P., Xi, Y., Lai, Y., Yang, S.: ACS Sustain. Chem. Eng. 7, 18228–18235 (2019)

22. 23. 24. 25. 26. 27. 28.

29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39.

40. 41. 42. 43. 44. 45. 46. 47.

9 Recycling of All-Solid-State Lithium-Ion Batteries

273

48. Heelan, J., Gratz, E., Zheng, Z., Wang, Q., Chen, M., Apelian, D., Wang, Y.: J. Mater. Sci. 68, 2632–2638 (2016) 49. Anari, H.B.E., Boschin, A., Mandai, T., Masu, H., Poulsen, K.M., Johansson, P.: RSC Adv. 6, 85194–85201 (2016) 50. Tsai, C.L., Ma, Q., Dellen, C., Lobe, S., Vondahlen, F., Windmüller, A., Grüner, D., Zheng, H., Uhlenbruck, S., Finsterbusch, M.: Sustain. Energy Fuels 3, 280–291 (2019) 51. Helbig, C., Bradshaw, A.M., Wietschel, L., Thorenz, A., Tuma, A.: J. Clean. Prod. 172, 274–286 (2018) 52. Piana, G., Ricciardi, M., Bella, F., Cucciniello, R., Proto, A., Gerbaldi, C.: Chem. Eng. J. 382, 122934 (2020) 53. Schwich, L., Küpers, M., Finsterbusch, M., Schreiber, A., Rohlfing, D.F., Guillon, O., Friedrich, B.: Metals 10, 1523 (2020) 54. Zhang, N., Long, X., Wang, Z., Yu, P., Han, F., Fu, J., Ren, G., Wu, Y., Zheng, S., Huang, W., Wang, C., Li, H., Liu, X.: ACS Appl. Energy Mater. 1, 5968–5976 (2018) 55. Xiao, J., Li, J., Xu, Z.: J. Hazard. Mater. 338, 124–131 (2017) 56. Wang, Y.Y., Diao, W.Y., Fan, C.Y., Wu, X.L., Zhang, J.P.: Chemistry 25, 8975–8981 (2019) 57. Uhlenbruck, S., Dornseier, J., Lobe, S., Dellen, C., Tsai, C.L., Gotzen, B., Sebold, D., Finsterbusch, M., Guillon, O.: J. Electroceram. 38, 197–206 (2017) 58. Ken, H., Greinerstraat, A.: Acta Metallurgica Slovaca 12, 111–120 (2006) 59. Maschler, T.G., Friedrich, B., Weyhe, R., Heegn, H., Rutz, M.: J. Power Sources 207, 173–182 (2012) 60. Xue, Z., He, D., Xie, X.: Poly(ethylene oxide)-based electrolytes for lithium-ion batteries. J. Mater. Chem. A 3, 19218–19253 (2015). https://doi.org/10.1039/C5TA03471J 61. Gaines, L.: Sustain. Mater. Technol. 17, e00068 (2018) 62. Gratz, E., Sa, Q., Apelian, D., Wang, Y.: J. Power Sources 262, 255–262 (2014) 63. Elwert, T., Goldmann, D., Romer, F., Buchert, M., Merz, C., Schueler, D., Sutter, J.: Recycling 1, 25–60 (2016) 64. Shao, C., Liu, H., Yu, Z., Zheng, Z., Sun, N., Diao, C.: Solid State Ion. 287, 13–16 (2016) 65. Pehlivan, I.B., Marsal, R., Niklasson, G.A., Granqvist, C.G., Geore´, N.P.: Solar Energ. Mater. Solar Cells 98, 2399–2404 (2010) 66. Chen, W.S., Ho, H.J.: Metals 8, 321 (2018) 67. Zheng, X., Gao, W., Zhang, X., He, M., Lin, X., Cao, H., Zhang, Y., Sun, Z.: Waste Manag. 60, 680–688 (2017) 68. Barik, S.P., Prabaharan, G., Kumar, L.J.: Cleaner Prod. 147, 37–43 (2017) 69. Aaltonen, M., Peng, C., Wilson, B.P., Lundström, M.: Recycling 2(4), 20 (2017) 70. Gao, W., Zhang, X., Zheng, X., Lin, X., Cao, H., Zhang, Y., Sun, Z.: Environ. Sci. Technol. 51, 1662–1669 (2017) 71. Zeng, X., Li, J., Shen, B.J.: J. Hazard. Mater. 295, 112–118 (2015) 72. Moeller, T., Kremers, H.E.: J. Phys. Chem. 48(6), 395–406 (1944) 73. Kobayashi, T., Sasaki, T., Takagi, I., Moriyama, H.J.: Nucl. Sci. Technol. 44, 90–94 (2007) 74. Tan, D.H., Xu, P., Yang, H., Kim, M.C., Nguyen, H., Wu, E.A., Doux, J.M., Meng, Y.S., Chen, Z.: MRS Energy Sustain. 7 (2020) 75. Shi, Y., Chen, G., Chen, Z.: Green Chem. 20, 851–862 (2018) 76. Palaniyandy, N., Rambau, K., Musyoka, N.: J. Ren. J. Electrochem. Soc. 167, 090510 (2020) 77. Shi, Y., Chen, G., Liu, F., Yue, X., Chen, Z.: ACS Energy Lett. 3, 1683–1692 (2018) 78. Peng, C., Kamiike, Y., Liang, Y., Kuroda, K., Okido, M.: ACS Sustain. Chem. Eng. 7, 10751– 10762 (2019) 79. Zhang, Q., Cao, D., Ma, Y., Natan, A., Aurora, P., Zhu, H.: Adv. Mater. 31, 1901131 (2019) 80. Tan, D.H., Banerjee, A., Chen, Z., Meng, Y.S.: Nat. Nanotechnol. 15, 170–180 (2020) 81. Chen, S., Xie, D., Liu, G., Mwizerwa, J.P., Zhang, Q., Zhao, Y., Xu, X., Yao, X.: Energy Storage Mater. 14, 58–74 (2018) 82. Meng, X., Hao, J., Cao, H., Lin, X., Ning, P., Zheng, X., Chang, J., Zhang, X., Wang, B., Sun, Z.: Waste Manage. 84, 54–63 (2019) 83. Wang, Y.Y., Diao, W.Y., Fan, C.Y., Wu, X.L., Zhang, J.P.: Chem. Eur. J. 25, 8975–8981 (2019)

274

K. Ajith et al.

84. Haack, J.M., Lenk, W., Lehmann, D., Lunkwitz, K.: J. Membr. Sci. 184, 233–243 (2001) 85. Catton, J.W.A., Walker, S.B., McInnis, P., Fowler, M., Fraser, R.A., Young, S.B., Gaffney, B.: Batteries 5, 14 (2019) 86. Omar, N., Monem, M.A., Firouz, Y., Salminen, J., Smekens, J., Hegazy, O., Gaulous, H., Mulder, G., Bossche, P.V.D., Coosemans, T.: Appl. Energy 113, 1575–1585 (2014) 87. Lu, L., Han, X., Li, J., Hua, J., Ouyang, M.: J. Power Sources 226, 272–288 (2013) 88. Cao, Z., Zheng, X., Cao, H., Zhao, H., Sun, Z., Guo, Z., Wang, K., Zhou, B.: Chem. Eng. J. 337, 256–264 (2018) 89. Wolfenstine, J., Allen, J.L., Read, J., Sakamoto, J.: J. Mater. Sci. 48, 5846–5851 (2013)

Chapter 10

Future Challenges to Address the Market Demands of All-Solid-State Batteries K. P. Abhilash, P. Nithyadharseni, P. Sivaraj, D. Lakshmi, Seema Agarwal, Bhekie B. Mamba, and Zdenek Sofer

10.1 Introduction The improvements in ASSBs are highly desirable for its widespread adoption in electric automobile industry consisting of Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs) [1]. It has been expected that by the end of next decade around 140 million EVs will be proceeding in the roads over the world [1]. The all solidstate lithium-ion batteries (ASSLIBs) are considered as the major contributors for K. P. Abhilash (B) · Z. Sofer Department of Inorganic Chemistry, University of Chemistry and Technology Prauge, Technická 5, 166 28, Prague 6, Czech Republic e-mail: [email protected] Z. Sofer e-mail: [email protected] P. Nithyadharseni (B) Institute for the Development of Energy for African Sustainability (IDEAS), College of Science, Engineering, and Technology (CSET), University of South Africa, Florida Science Campus, Roodepoort 1709, South Africa e-mail: [email protected] P. Sivaraj · S. Agarwal Bavarian Center for Battery Technology, Macromolecular Chemistry II, University of Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany e-mail: [email protected] D. Lakshmi Department of Physics, PSG College of Arts and Science, Coimbatore, India e-mail: [email protected] B. B. Mamba Institute for Nanotechnology and Water Sustainability (iNanoWS), College of Science Engineering and Technology (CSET), University of South Africa, Florida Science Campus, Roodepoort, South Africa e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 N. Palaniyandy et al. (eds.), Solid State Batteries, Advances in Material Research and Technology, https://doi.org/10.1007/978-3-031-12470-9_10

275

276

K. P. Abhilash et al.

the HEVs and EVs industries worldwide. However, the R&D department is highly demanding new materials and new technologies for the intense development. The short time span run for a single charging is considered as one of the major challenges to be overcome for building better battery technology for futuristic EVs and HEVs industry [2]. The high power and energy density are considered as other major factors that should be achieved for a better ASSB technology. The increase in energy densities of the individual components and the increase in total energy density of the battery pack should be concentrated to achieve this goal. The compact stacking of the battery components within smaller area is an ideal method for increasing the total energy density. But in most of the cases, this strategy will not work. The compact packing will develop more pressure to the individual components, which will result in serious safety problems in ASSBs. The solid-electrolytes exhibit very high potential window, when compared with the liquid electrolytes. The parasitic reactions at certain range of voltages in ASSBs may create serious cycling degradation over aging in ASSBs. Hence, the very high potential window with safer operation is highly desirable for the development of high-density ASSBs [3]. The safety comes as a major challenge, for the futuristic development of ASSBs to a large extend. The explosion risks in EVs and HEVs are more horrendous than that of any other application perspectives of ASSBs. In terms of safety, compared with the batteries using liquid electrolytes, ASSBs are the best choice for the EVs and HEV industry, with its intrinsic high safety profile for a long duration of time [1, 4]. Even then, the battery swelling and high parasitic side reactions in the ASSB interfaces make serious safety issues for the large-scale market development of ASSBs [5]. Attaining the high ionic conductivity in the range of superionic conductors is believed to be the criteria for attaining better Li-ion intercalation in ASSBs, which in turn results in better battery performances [1, 5]. Many of the organic and inorganic solid electrolytes that reported in the recent period of time show high ionic conductivity, comparable with the liquid electrolytes [6, 7]. Some of the sulfide and oxide type solid-electrolytes exhibit exceptional ionic conductivity, for its potential application in ASSBs. In addition to this, the ASSBs mainly suffer from serious issues regarding the poor performance of the solid–solid interfaces [3]. The high charge transfer impedance that developed at the solid–solid interfaces region of ASSBs is one of the major huddles for the safer cycling of ASSB assemblies. The intimate contact at the solid–solid interfaces is considered as one of the major requisites for the facile ionic movement across the region of interfaces in ASSBs. Very high impedance developed at the region of interfaces is considered as one of the major huddles for the facile ionic movement across the interfaces in ASSSBs [8]. Along with these factors, the higher mechanical strength is yet another factor that required for developing safe ASSBs for its large-scale market implementations. The scarcity of the characterization tools deep inside the solid–solid interface layers is considered as one another major limiting factor to identify the failure mechanism of ASSB assemblies. The development of suitable characterization methods and

10 Future Challenges to Address the Market Demands …

277

strategies is highly desirable for the large-scale implementation of ASSBs over the markets. The cost-effective assembly of ASSBs is the target of the automotive industry to reduce the total cost of the EVs and HEVs in the market. The demand of the electronics industry was in smaller scale, when compared with the automotive industries. Hence, large-scale manufacturing in most cost-effective manner is considered as a major challenge for the assembly of ASSSBs for automotive industry [2]. Fast-charge capability without disturbing the chemistry of the electrode and solidelectrolyte material is considered as the dream requirement of the ASSBs market. The fast-charging and safety should be properly conjugated to result in better ASSB assemblies. The electrified transportation industry and the grid line energy storage chemistries are mainly evaluated by means of life, energy density, cost-effectiveness, safety, and fast charge–discharge capability of the battery system [2]. The electrified transportation industry applications propose more rigorous technical necessities such as long calendar life around 15 years, cycle life more than 1000 cycles, wide temperature range for operation from − 40 to 85 °C, and cost-effective preparation [2]. Parameters such as voltage stability, as well as catastrophic breakdown of the batteries by shorting, form yet other challenges before the material scientists [9, 10]. Many of the companies have been dedicated their efforts for the widespread commercialization of all-solid-state Li batteries in electronic devices, electric vehicles (HEVs and EVs), comprising Tesla, Solid Energy, Toyota, Seeo, Infinite Power Solution, Quantum Scape, Sakti3, Front Edge Technology Inc., Bolloré, and so on [11]. The Bolloré (France) has used the all-solid-state lithium batteries used in electric vehicles for the first of its kind in 2011 [11]. But the advanced all-solid-state batteries are still under the stage of research and development. Some of the electronic companies like HP and Dell reported some battery catastrophe. Various automobile companies like Tesla, Ballore, Fisker, etc. have also reported some battery explosion at different stages [12]. The explosion of the polymer electrolyte of ASSB assembly used in an Avester’s product shows another example for fire incident with batteries [12]. This incident points that the safety forms a major challenge for the commercialization of ASSB assemblies in the market level. The global automotive industry is trying hard to get rid of its intense addiction on petroleum technologies and moving towards to make some long-lasting technological change by the electrified transportation industry [13]. There are many engineering challenges that limit the growth of the market of ASSBs. In order to address the challenges that faced by the ASSB assemblies, an in-depth knowledge on the technological failures and the industrial requirements are highly anticipated.

278

K. P. Abhilash et al.

10.1.1 Market Demands to Be Fulfilled with ASSBs The battery markets all over the world are facing grand challenge due to the massive requirement of the batteries for the EVs and other electronic gadgets that proliferate day by day. The EV industry demands the cost reduction in the overall battery assembly, so that the industry can provide the EVs in affordable price as gasoline vehicles [13]. The fulfillment of the market demands is only possible by the correlative research on the fundamental battery materials analysis, specific electrochemical testing, and the innovative designing of the battery packs in more cost-effective manner. Different kinds of electric vehicles are now a days available in the market such as, full batterypowered electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs) and so on. The Johnson Controls Inc (JCI) announced the development of different batteries that suitable for HEVs in the last decade [14]. The company in collaboration with Toshiba Infrastructure Systems & Solutions Corporation have announced to deliver low-voltage lithium-ion solutions to meet the demands of automakers to obtain enhanced efficiency, cheaper in cost and less intricacy[14]. Sales of the first series Production of plug-in electric vehicles (cars) began in 2008, introducing the BYD F3DM plug-in hybrid, and the all-electric Mitsubishi i-MiEV in 2009. The world market demands around 140 million electric vehicles on road by the end of next decade. The academic and industrial research should proliferate, many fold enhancements to attain this summit. The solid-state battery markets deliver the highest energy density to the devices when compared with other battery technologies. Even though the energy density that is sufficient to reach the market demand necessitates still long way to go. The expected power and energy densities by the world battery scenario have been tabulated in the Scheme 10.1. The total shell life of the batteries makes another challenge for the battery industry for the commercialization of ASSBs in the market. The total life of any battery directly depends on its cycle life. More than 1000 cycles with minimum capacity degradation can be considered as a benchmark for the commercialization of batteries in the market. Above all, the safety is still considered as the prime concern for the largescale implementation of ASSBs in the market. The battery research demands, some advanced cathodes (especially), anodes, and highly conducting solid electrolyte with its conductivity falling in superionic conductor range (10–3 Scm−1 ). The costeffective manufacturing will only be possible by the introduction of some novel design strategies. The battery pack optimization is also deserved equal important as any other battery goals before the battery researchers. Recent studies clearly point out the fact that the research and development is lagging in the area of practical innovative cell designs, and its advanced characterization aspects than the material preparation and analysis [4]. The EV or HEV market demands the batteries that are highly abuse tolerant and long-lasting.

10 Future Challenges to Address the Market Demands …

279

Scheme 10.1 Challenges and market demands with ASSBs

10.2 Future Challenges with ASSBs 10.2.1 Challenges with the Existing Electrolytes The choice of resource materials for the arbitrating component of ASSB—solid electrolytes is limited up to the present verge of research such as ceramics and polymers. That is, the total systems of SEs available to date can be confined to oxide, sulfide, hydride, halide, and polymer materials. There are different pilot studies that have been reported on these materials as electrolyte components in the ASSB system but unresolved technical limitations emerge one over the other. The major problems faced by SEs in their role are, mechanical stability, chemical compatibility with fellow components, potential stability over the wide window, ionic conductivity, electronic insulation, and homogenous performance over a period. Figure 10.1 shows the comparative performances of different SE systems when employed in ASSBs [15]. Comparatively, the scope of the SE is not limited to inorganic or real solid materials whereas polymers also contribute to this application with their inherent limitations such as thermal stability and electrochemical stability window. Considering the oxide-based candidates such as LLTO, LIPON and LLZO, all the materials exhibit better compatibility with the common electrode materials except the fact that LLTO undergoes electronic conduction on interaction with Li metal. However, materials of these kinds are often dense and highly crystalline which naturally possess certain flaws such as Griffith flaws [12]. This needs careful cell design in order to overcome these geometrical factors such as optimization of SEs shear modulus at the interface, minimizing the inhomogeneous deposition and penetration of Li at the interface, stabilization of the electrolyte–electrode interface, and so on. In the case

280

K. P. Abhilash et al.

Oxide

Hydride

Sulfide

Halide

Polymer

Reduction Stability

Oxidation Stability

Chemical Stability

Thermal Stability

Mechanical Stability

Cost

Device Integration

Fig. 10.1 Comparative performances of different solid-state electrolytes in terms of their technical aspects

of sulfide-based electrolytes such as Thio-LISICON, the materials are often referred as softer units but this makes a strong correlation between ion migration entropy and activation energy of these conductors. Also, the shuttling effect of polysulfides on electrochemical process has to be considered. Often, the absence of long-range periodicity affects the reversibility and structural stability of SEs. The same goes for selenide systems. Other than softer framework, sulfide materials are not environmentally friendly to handle. On meeting the atmosphere or interaction with moisture content by any mode, end up in the creation of highly toxic component H2 S hence the sulfide components are being modified enormously such as by doping to fit into the actual frame of resources [12, 16, 17]. Amidst different SEs, sulfides and oxides play the prominent positions in this category hence modification of the cells fabricated with these types of SEs requires careful design of interface, which is another broad topic of discussion. Further systems such as hydrides, halides, and nitrides such as Li3 O(Cl/Br), LiBH4 and Li3 N also participate in the race but the processing time and reversibility are the main hindering factors. Especially, hydride material mentioned above decomposes above 300° C which questions its thermal window in a device. Other side, the nitride candidate is an excellent electrical conductor (~10–4 Scm−1 ) but possesses really a narrow potential window[16]. One more class such as organic–inorganic composites is also being experimented but it needs a deep sense of information and proof for

10 Future Challenges to Address the Market Demands …

281

understanding the working mechanism of this class [17]. Still, any candidate cannot be overlooked or neglected but a careful target towards the specific application and device assembly is crucial factors for extracting the virtues out of it. Overall, with the constant effort of the scientific community on SE research, the major issue associated with this class has been acknowledged well and is being researched to bring it to the practicality.

10.2.2 Challenges in Attaining High Energy Density Unlike commercial organic liquid electrolyte-based LIBs, ASSBs show the absence of passive cell components, which can directly impact the energy density of the cell. Still, this is conceptualized only in theories since multiple factors affect the end result of the systems. Few important aspects are mentioned here. Other than the established resource materials, the important hindrance in attaining the high energy density is the interfacial issues such as chemical incompatibility and poor physical contact. The chemical incompatibility between the active materials such as anode| SE| cathode is due to the structural/phase-related and composition related issues. Also, the volumetric disintegration of electrode materials on deep charge discharge cycle affects the mechanical contact between the electrode| electrolyte interface often deteriorating the overall device performance and energy density. On the other side, unfortunately, not all the materials which exhibit high electrical conductivity and wide potential window are stable with Li metal anode whereas Li metal is a crucial component for having high energy density (both gravimetric and volumetric). Often research cannot limit to the sole Li dependence for high energy density which leads to the variety of cathode materials and their optimization to the full device architecture. One among those is sulfide conducting material as composite matrix [18]. But, previously discussed issues such as softer framework and toxicity stop the realism of them. On the other side, the formation of heterogeneous space charge layer at the electrode–electrolyte juncture is highly resistive component, which induces poor battery performance [19] and descent in the energy density component by means of poor Li composition gradient. Another report suggests that excess Li supply is also a hindrance to the energy density of the cell [20]. Further, when Li-intercalating materials such carbonaceous and metal oxides are chosen as electrodes, they need a large room for device integration which limits the practical features. The other aspect is, these SEs work good in the bulk form but reducing their thickness pivot the lower interfacial resistance but on the back side it affects the mass content of the electrolyte material and hence the dendrites/ physical contact issues evolve. To overcome the issues associated with the high energy density anode, Li, usage of alloys such as Li-In, Na-Sn are being attempted in real solid systems [12]. The other component, cathode active materials, decides the working potential window and redox species, which connects the total energy density of the cell. The limited choice of cathode materials to the practical system is another setback in extracting

282

K. P. Abhilash et al.

the high energy density out of ASSBs. Yoshima et al. suggest bipolar packing of cells whereas one anode is stacked on the cathode of the other cell so that voltage of the cell is improved [21], which may provide increased energy density overall. However, this needs viable attempt to prove the concept. Taken as a whole, the limited energy density in SE cells than that of the expected values is mainly attributed to their interfacial chemistries and mechanical disruption through volume changes. Carefully engineered interface by means of simulated along with spontaneous interface/interphase regions such as by coating with active interlayers (Al2 O3 , LTO, pure metal layers, carbon coating, TiO2 etc.,) or optimized conformations (thin film/thick film/ stacking/ layered arrangements etc.,) can provide better cell operation and high energy density. Further, research has to be integrated to understand the material level energy density-cell level energy density and device level energy density so that design strategies and correlations between their performances in cell architecture can be simulated.

10.2.3 Challenges with the Effective Tools for Characterization Even though the battery market explodes day by day, the mainstream research in ASSB lag its advancement due to the lack of sophisticated characterization tools to probe the minute details of the interfaces and other important features of the assembly [22]. The available instruments as such cannot provide the nano-scale features that evolving at the region of solid electrode-solid electrolyte interfaces. Moreover, the in-depth fundamental understanding of the potential or current distribution profiles and the accumulation of the heavy ions at the region of interfaces are highly desirable, since it can be the deciding factor for the facile electrochemical intercalation of the Li ions across the electrolyte [23]. The advanced in-situ and operando techniques (transmission electron microscopy (TEM), X-ray absorption spectroscopy (XAS), X-ray powder diffraction (XRD), and other spectroscopy methods working in operando mode) along with the modeling techniques give some clue on the interfacial chemistry and mechanisms of ionic conduction [24, 25]. The features leading to the dendrite formation and other interfacial products are still not fully known. However, the in-situ and operando techniques are helpful to understand some important interfacial issues, by properly analyzing the initial cycling stages of the batteries. Moreover, deep fundamental understanding of the potential profile and its distribution across the interface can be obtained by employing some recent advanced characterization approaches [7]. Understanding the electrolyte–electrode interface and improving the properties with nano-engineering and new materials identification is absolutely necessary for constructing a safe Li battery with enriched electrochemical performance. The realtime analysis of atomic scale interface evolution occurring in ASSBs has vast importance to give the deep information on the cyclability of the assembly.

10 Future Challenges to Address the Market Demands …

283

The TEM and STEM instruments have been effectively utilized by many of the researchers to achieve the minute details of the interface morphology and elemental distribution [26]. The microstructural analysis using the cryo-TEM gives the minute details such as the SEI layer formation during the initial cycling of the batteries. The STEM can be considered as an effective tool to probe many of the interfacial features like the reason for the additional impedance developed at the region of interface, structural variations of the compounds, and so on. The STEM measurements can be coupled with many of the other characterization techniques such as electron energy loss spectroscopy (EELS), 3D holographic recording techniques, etc. [27]. The qualitative and quantitative measurements are possible with this technique [8]. The uniform potential distribution across and along the interfaces in ASSBs is highly important for the facile movement of ions from one electrode to other one. The identification of the potential distribution profile is an important approach to elucidate the factors affecting the potential distribution. The sudden drop in the potential at some regions leads in high impedance for the charge flow at that region [28]. The identification of Li insertion extraction at the interface in real time gives proper indication about the cycling of the batteries. The studies presented by Kazuo Yamamoto and co-workers reveal the details on potential distribution due to lithium ions across a LiCoO2 electrode/solid-electrolyte interface during cycling reactions for the first of its kind [8]. The X-ray-related advanced characterization techniques are also highly helpful tools to identify the composition and identification of the impurity contends that produced due to the side reactions at the region of interface. The morphological and structural information of the samples can be identified by coupling the XRD and transmission spectroscopic techniques. The transmission X-ray imaging (TXM) can elucidate the minute microstructure along with the sample morphology. Nowadays, TXM-XANES is considered as most effective tool for the real-time special mapping within the sample at different portions including the interfaces. Along with the structural and morphological features, the real-time analysis on the evolution of the electrochemical processes is also highly imperative in ASSBs. B. L. Mehdi et al. have reported the quantification of nanoscale processes that occur at the batteries by a novel operando electrochemical STEM process. They could identify the solid electrode-solid electrolyte interface SEI formation by employing this method. The method is scalable for different electrochemical characterization techniques [29]. Chuang Yu et al. analyzed the Li-ion transport across the interface in Li2 S cathode and Li6 PS5 Br solid electrolyte using the 2D Li-ion exchange NMR technique (Li 2D EXSY) [30]. The spontaneous Li-ion transport rate at the interface under different sample preparation conditions has been analyzed in which they illustrate that the electrochemical cycling strongly depends on the interfacial conductivity, which in turn directly depends on the intimate interfacial contact and diffusion barriers [30]. Figure 10.2 illustrates that the method of sample preparation, like ball milling and reduction of particle size, improves the spontaneous lithium ions exchange at the region of interface. This in-situ NMR technique is highly useful when studying the spontaneous movement of Li-ion in ASSBs.

284

K. P. Abhilash et al.

Fig. 10.2 Interfacial spontaneous Li-ion transport analysis between the Li6 PS5 Br solid electrolyte and the Li2 S cathode in ASSBs using the 2D Li-ion exchange NMR technique. (a, e, i) One-dimensional (1D) 7 Li magic angle spinning (MAS) spectra for Li6 PS5 Br–Li2 S cathode mixtures (a) mixture I, in which Li2 S is micron-sized (e) mixture II, in which Li2 S is nanosized (i) mixture III, in which nanosized Li2 S is thoroughly mixed with Li6 PS5 Br. 2D 7 Li–7 Li exchange spectra (2D-EXSY) at a 7 Li resonance frequency of 155.506 MHz and a spinning speed of 20 kHz, recorded for three mixtures (b–d, f–h and j–l). The figure adopted from the reference [30], with the permission from Springer Nature (2017)

The proper identification and utilization of the electrode–electrolyte interface characterization tools at nanoscale requires further intense research and in-depth scientific knowledge about the interface characteristics and device management. The advanced STEM- and TEM-based in-situ and in-operando type techniques provide vital information on the battery operations and interface stability. The dynamic in-situ electronic potential distribution profile analysis is considered as one of the effective strategies to analyze the intense electrode/electrolyte interface formation and ionic movement across the interfaces [23].

10.2.4 Challenges in the Design Aspects The design of novel battery configuration is one of the unique advantages of solidstate battery for its potential applications. The thickness of the solid-state electrolyte

10 Future Challenges to Address the Market Demands …

285

layer and the electrodes is highly desirable factor for a novel design with high energy density and in reducing the total battery cost. The stacking of the solid electrolyte layer that internally connected to multiple battery cells is an effective method for decreasing the cost. The common design strategy involves the staking of Li containing, a layer of cathode and solid electrolyte composite, then a layer of anode with or without a Li content, stacked one over the other in a 3D fashion [4]. The lagging of novel stacking strategies in ASSBs leads to the wastage of energy to a large extend, which will result in poor energy/power density of the assembly. Some of the other stacking strategies that employing in the R&D and in the industrial level have been displayed in Fig. 10.3. Some of the companies devoted their effort to utilize the advantages of new electrolyte chemistries along with the novel design aspects for the industrial commercialization of their batteries. The Fuji film Company developed one inorganic sulfide electrolyte. Along with the development of electrolytes, the Company grasped some novel technologies, on the design aspects such as roll to roll process (as multi-layers),

Fig. 10.3 Stacking of the main cell architectures utilized in solid-state battery research a ASSB configuration utilizing the cathode interfaced with a solid electrolyte and anode; b a hybrid method employing a liquid or polymer-based cathode interfaced with a solid electrolyte and anodes with high energy density; and c anode free design. Here the cell is constructed with only a cathode and separator, then the metal anode is formed upon first charge. The figure has been adopted from the Ref. [12] with the permission of Electrochemical Society (2017)

286

K. P. Abhilash et al.

utilization of coated film electrodes, and making the strong bonding between the electrode and electrolyte [11]. The major challenges with the stacking include; mechanical strength achievement, viability of large-scale production, cost-effectiveness and difficulty in achieving longterm cycling. Any of the proposed design strategy should mainly focus on the aforementioned viewpoints to accomplish the goal of a successful long-lasting stacking model for ASSBs. The very high pressure that developed from stacking should be alleviated properly for the long-term cycling of the cells. Some of the stacking strategies, even if it increases the area of interface and retains maximum capacity at the expense of its mechanical strength. This mainly affects the batteries in its long-term run. Sometimes it may also result in short-term total breakdown of the cell. The high energy density of the battery necessitates more cathode component in the battery stacking when compared with all other components. The usage of cathode composites to easily adopt the volume change that produced by the solid electrolytes in ASSBs can produce intimate interface contact in ASSBs [31]. Figure 10.4. represents an ideal way of stacking, with thick cathode layer for attaining high energy density for the solid-state pack. The intimate contact between the electrode and electrolyte material is considered as the major pre-requisite for any type of stacking. The intimate contact with maximum contact area can be visualized in nano-nano interface designs and 3D flexible interface design strategies. Another center of interest is the proper alleviation of Fig. 10.4 An ideal way of stacking including a thick cathode, a thin separator, thin Li anode which expands on charging, and thin current collectors at anode and cathode side to obtain high-energy solid-state battery pack. The figure reproduced from reference [4], with the permission from American Chemical Society, (2021)

10 Future Challenges to Address the Market Demands …

287

the volume change that usually occurs over long-term cycling. The fruitful design to include the volume expansion of the electrode and solid electrolyte material will certainly improve the long-term cyclability of the cell. The design strategy should also placate the parasitic reactions and dendrite growth that occurs in the cell in its long-term usage.

10.2.5 Challenges with the Stability of the Batteries The mechanical, thermal, chemical and electrochemical stability of multilayer composite systems of SSBs are critical for achieving high cycling and calendar life. The stability of the electrolyte and its interfaces with both the cathode and the anode should be considered while designing SSEs for mass production of SSBs.

10.2.5.1

Mechanical Stability

Mechanical stability is the most important characteristic in mass production (Fig. 10.5a). The composite SSEs should have mechanical qualities suitable for scalable cell manufacture, be able to buffer volume changes during charge–discharge cycling, and inhibit Li-dendrite growth. In theory, a solid and dense electrolyte membrane (free of porosity and grain boundaries) with a shear modulus greater than 6 GPa can prevent the formation of Li dendrites. Because flexible polymer electrolytes have low shear moduli (usually 0.1 GPa), blocking Li dendrites is challenging [32, 33]. Inorganic electrolytes can have shear moduli in the tens of gigapascals (60 GPa for LLZO) [34]. One of the initial goals of developing composite SSE (CSSE) was to improve the mechanical strength of polymer electrolytes. When compared to the polymer matrix, the addition of inorganic filler increases tensile strength but decreases elongation-at-break. Choosing a polymer with high viscoelasticity, selfhealing ability, and film forming ability can result in a CSSE having high mechanical stability. The mechanical characteristics of CSSE are also affected by the inorganic filler and its concentration. Because of the substantial amount of ceramic fillers in-polymer electrolytes have excellent flexibility; however, polymer-in-ceramic electrolytes have poor flexibility (Fig. 10.5a) and adhesion properties. Inadequate adhesion might impede with the strong contact between the electrode and the electrolyte, resulting in high interfacial resistance during cycling. As a result, the rational design of SSEs requires a balance between achieving a suitable modulus and adequate surface adhesion to both the cathode materials and the Li-metal anode. The preparation of CSSE with a thin, soft, and sticky surface of a polymer electrolyte [35] in which the soft and adhesive polymer layer creates better contact with the cathode active surface and the stiff CSSE surface has superior mechanical properties and inhibits Li dendrites. Of course, increasing the shear moduli of CSSEs will not totally fix the Li-dendrite problem. Dendrites could form along the grain boundaries of ceramics at a particular

288

K. P. Abhilash et al.

Fig. 10.5 a Mechanical stability—Strain vs Stress curves; b thermal stability-TGA curves; c chemical stability—materials that are susceptible to ambient air and moisture, such as LLZO and sulfides; d electrochemical stability of different SSEs

current density even in rigid ceramic electrolytes with a high shear modulus, such as LLZO [36]. As recently proposed chemomechanical design rules[37] demonstrate, a high modulus is not required for reducing dendritic formation.

10.2.5.2

Thermal Stability

The thermal stability of SSEs is critical for battery safety. Most inorganic electrolytes are viable at significantly higher temperatures, and polymer-based SSEs generally decompose at temperatures beyond 300 °C (Fig. 10.5b). The thermal stability of polymer electrolytes is greater than that of liquid electrolytes; however, the addition of Li salts lowers the degradation temperature. As a result, adding inorganic fillers to a polymer electrolyte can improve thermal stability [38] because the fillers serve as a skeleton and maintain the integrity of CSSEs at high temperatures. Even though the polymer portion breaks, the inorganic framework keeps the electrodes apart. The formation of an appropriate ratio of inorganic electrolyte and polymer composite is a promising strategy for improving thermal stability and ionic conductivity; however, their concentration must be controlled, and their safety must be evaluated in largescale production of SSBs.

10 Future Challenges to Address the Market Demands …

10.2.5.3

289

Chemical Stability

The chemical stability of SSEs depends on storage and production conditions, as well as the choice of appropriate electrode materials. It can be determined by contacting the electrolyte with the active anode and cathode materials. Materials that are susceptible to ambient air and moisture, such as LLZO and sulfides (Fig. 10.5c), would result in high fabrication costs and safety problems. Polymer-based SSEs typically have strong chemical stability in air but must be handled in a dry environment to avoid H2 O absorption. CSSEs should be compatible with the electrodes for SSBs, with no disastrous and irreversible chemical side reactions forming between an electrolyte and the electrodes over the full storage and service lifetime. Even if an interface cannot be created thermodynamically stable, it should be rendered kinetically stable [39]. CSSEs have chemical stability similar to the polymer matrix in most circumstances. In rare situations, inorganic fillers may capture residues of H2 O or solvents at their surfaces, inhibiting H2 O or solvent interaction with the Li anode. It is important to note that, inside CSSEs, the polymer component can serve as a buffer layer to inhibit direct contact and the harsh interaction of inorganic electrolytes (LATP and LLTO) with the Lithium anode. The sulfide-based CSSEs consist of sulfide particles encased in a polymer, the interfacial interaction between the sulfide particles and the Li anode is prevented [40]. As a result, more attention should be paid to designing a SSE to decrease the chemical instability of inorganic components towards Li metal by minimizing direct contact between the components.

10.2.5.4

Electrochemical Stability

The electrochemical stability of SSEs is represented by the electrochemical stability window (Fig. 10.5d), its compatibility with high-voltage cathode materials and the Li-metal anode is critical for achieving high-energy–density SSBs. Inorganic SSEs have broad electrochemical stability windows, with upper limits exceed the polymer and liquid electrolytes [41]. The intrinsic electrochemical windows of inorganicelectrolyte materials have been studied experimentally and theoretically by examining the thermodynamics of the electrolyte–electrode interfaces. Polymer-based electrolytes gradually oxidize at voltages above 3.8 V, limiting their use in highenergy–density batteries. Furthermore, polymers (most commonly PEO) and Li salts are hygroscopic, and if the polymer electrolyte is polluted with moisture during the production process, it becomes more unstable[42]. Hence, the addition of filler particles results in broader electrochemical stability windows for CSSEs than for polymerbased SSEs (Fig. 10.5d) [43]. Nonetheless, further research is required to determine the mechanism of this broadening effect. More research should be conducted to develop CSSEs using a polymer matrix, Li salt, and inorganic fillers in order to broaden the electrochemical stability windows. Because of the nitrogen-containing functional group, nitrile-based polymers (for example, PAN) exhibit superior antioxidative performance, and employing PAN as the polymer matrix can result in a CSSE with a high oxidation potential [44]. The anodic stability of the CSSE in

290

K. P. Abhilash et al.

the composite cathode may change because the active components can catalyze the oxidative degradation of the electrolyte. For example, layered active oxide materials could cause decomposition of PEO or the Li salt in PEO-based CSSE [45]. The practical electrochemical stability of the system is determined by the interfacial reactions between the electrolyte and the electrodes. Aside from logical CSSE design, electrolyte–electrode interfaces can be designed to increase effective electrochemical stability.

10.2.6 Difficulties with Mass Production, Manufacturing Cost in High Energy/Power ASSBs State-of-the-art Li-ion batteries are facing their energy–density constraints and are being challenged by the ever-increasing requirements of today’s energy-storage applications. The energy-storage market for future electric vehicles requires a specific energy of more than 500 Wh kg−1 at the cell level, as well as a cheaper price. So far, numerous companies throughout the world have been working on the launch of SSB products, including Toyota, Volkswagen, and Samsung from the automotive and battery industries and the mass production of SSBs is expected in the next few years [46, 47]. To accomplish massive and low-cost SSB production, it is preferable to adapt the mature manufacturing platform used for Li-ion battery production, which includes slurry casting and roll-to-roll technologies, to produce SSBs. Nonetheless, such strategy depends on the development of solid electrolytes that are compatible with roll-to-roll processing [48]. Because SSB structure is similar to that of regular Li-ion batteries, it can be manufactured using conventional mass-production procedures. To reduce costs and achieve mass production of SSBs, the fabrication process could be intended to be similar to that used for conventional Li-ion battery manufacturing, such as continuous slurry casting and roll-to-roll processing of the polymer composite electrodes [49] and solid electrolyte separator, laminating, and stacking. The requirement for low-temperature processing to generate dense multilayered, multiphase composite structures suggests that soft and flexible solid electrolytes are suitable for large-scale and continuous SSB manufacture [50] (Table 10.1). As a nutshell, unlike normal Li-ion battery mass manufacturing, there will be no single technological process chain for mass manufacture of SSB cells. Rather, depending on the solid electrolyte used, several methodologies have been employed to manufacture SSB cells. There are two major difficulties to address in order to achieve and accelerate the implementation of SSB technologies. First, at the composite stage, the ion-transport characteristics and various stabilities of SSEs and composite electrodes must be improved. This enhancement necessitates the design and selection of the optimal inorganic and polymer material combination (particularly polymer electrolytes). Furthermore, there are numerous unanswered problems, such as the fundamental knowledge of the Li-ion transport pathway, internal dynamics, and macroscopic

10 Future Challenges to Address the Market Demands …

291

Table 10.1 Comparison of the characteristic properties of different types of electrolytes Type of SSE

Flexibility

Interfacial functionality

Thermal stability

Manufacturing feasibility for large-scale production of ASSBs

Ionic conductivity

Oxide

Poor

Poor

Excellent

Poor

Good

Sulfide

Moderate

Good

Good

Moderate

Excellent

Polymer

Excellent

Excellent

Poor

Excellent

Poor

Composite

Excellent

Good

Moderate

Excellent

Good

features of the multiphase SSEs networks of SSB cells. Addressing these problems will demand the integration of fabrication and characterization with simulations at various length and time scales. Sophisticated characterization methods must be used to study and record hidden interfaces in SSEs, synergistic interactions between many components, and contacts between SSEs. The fabrication of composite electrodes and the CSSE separator, as well as the laminated construction of an SSB cell with rational design of the two interfaces between the SSE separator and electrode layers, are critical to attaining high performance at the cell level. For rapid iteration and upgrading of fabrication techniques, novel scalable strategies should be employed to the fabrication, processing, and handling of composite electrode layers and CSSE separator layers for SSB cells, as well as tuning of layer thicknesses (thin electrolyte and Li-metal anode). The future of SSBs will be determined by automated cell fabrication and quality control of such laminated, multiphase SSEs/CSSEs. Although SSEs can significantly increase battery safety, the safety of big SSB modules and packs requires extensive testing before SSE-based SSBs are issued to the market.

10.3 Concluding Remarks The mitigation of different challenges by the smart battery management systems is the need of the hour for the large-scale implementation of the ASSBs to the market end. The smart battery management tools along with the battery management software can be utilized to figure out the challenges and its timely managements [51]. Different battery protection tools can be employed by allocating minimal space storage within the battery assemblies. The separators for battery short circuits/shutdown, safety diodes, temperature sensors, and vents are considered as some battery management tools. High temperature withstanding steel claddings and proper vent to deteriorate the challenges related with high volume expansion over long-term cycling are considered as yet other strategies to mitigate the challenges. The software monitoring and protecting sensor channels can be employed with the batteries. On the other hand, these protecting circuits or challenge management

292

K. P. Abhilash et al.

systems still increase the size of the total assemblies to a large extend. The costeffective manufacturing of ASSBs still needs a lot of research knowledge on the chemistry of different electrode and electrolyte materials. The development scenario of current solid-state battery technology demands a path change in a new, alternative way to explore more the material stacking and engineering controls to preserve the safe operation in its forthcoming applications. Acknowledgements K. P. A. was supported by the European Structural and Investment Funds, OP RDE funded project ’CHEMFELLS IV’ (No. CZ.02.2.69/0.0/0.0/20_079/0017899. Z. S. was supported by ERC-CZ program (project LL2101) from Ministry of Education Youth and Sports (MEYS).

References 1. Sun, Y.-K.: Promising all-solid-state batteries for future electric vehicles. ACS Energy Lett. 5(10), 3221–3223 (2020). https://doi.org/10.1021/acsenergylett.0c01977 2. Masias, A., Marcicki, J., Paxton, W.A.: Opportunities and challenges of lithium ion batteries in automotive applications. ACS Energy Lett. 6(2), 621–630 (2021). https://doi.org/10.1021/ acsenergylett.0c02584 3. Lim, H.-D., Park, J.-H., Shin, H.-J., Jeong, J., Kim, J.T., Nam, K.-W., Jung, H.-G., Chung, K.Y.: A review of challenges and issues concerning interfaces for all-solid-state batteries. Energy Storage Mater. 25, 224–250 (2020). https://doi.org/10.1016/j.ensm.2019.10.011 4. Albertus, P., Anandan, V., Ban, C., Balsara, N., Belharouak, I., Buettner, J., Chen, Z., Daniel, C., Doeff, M., Dudney, N.J., Dunn, B., Harris, S.J., Herle, S., Herbert, E., Kalnaus, S., Libera, J.A., Lu, D., Martin, S., McCloskey, B.D., McDowell, M.T., Meng, Y.S., Nanda, J., Sakamoto, J., Self, E.C., Tepavcevic, S., Wachsman, E., Wang, C., Westover, A.S., Xiao, J., Yersak, T.: Challenges for and pathways toward li-metal-based all-solid-state batteries. ACS Energy Lett. 6(4), 1399–1404 (2021). https://doi.org/10.1021/acsenergylett.1c00445 5. Scrosati, B., Garche, J.: Lithium batteries: status, prospects and future. J. Power Sources 195(9), 2419–2430 (2010). https://doi.org/10.1016/j.jpowsour.2009.11.048 6. Kamaya, N., Homma, K., Yamakawa, Y., Hirayama, M., Kanno, R., Yonemura, M., Kamiyama, T., Kato, Y., Hama, S., Kawamoto, K., Mitsui, A.: A lithium superionic conductor. Nat. Mater. 10(9), 682–686 (2011). https://doi.org/10.1038/nmat3066 7. Kato, Y., Hori, S., Saito, T., Suzuki, K., Hirayama, M., Mitsui, A., Yonemura, M., Iba, H., Kanno, R.: High-power all-solid-state batteries using sulfide superionic conductors. Nat. Energy 1(4), 16030 (2016). https://doi.org/10.1038/nenergy.2016.30 8. Ohta, N., Takada, K., Zhang, L., Ma, R., Osada, M., Sasaki, T.: Enhancement of the high-rate capability of solid-state lithium batteries by nanoscale interfacial modification. Adv. Mater. 18(17), 2226–2229 (2006). https://doi.org/10.1002/adma.200502604 9. Richards, W.D., Miara, L.J., Wang, Y., Kim, J.C., Ceder, G.: Interface stability in solid-state batteries. Chem. Mater. 28(1), 266–273 (2016). https://doi.org/10.1021/acs.chemmater.5b0 4082 10. Sharafi, A., Meyer, H.M., Nanda, J., Wolfenstine, J., Sakamoto, J.: Characterizing the Li– Li7La3Zr2O12 interface stability and kinetics as a function of temperature and current density. J. Power Sources 302, 135–139 (2016). https://doi.org/10.1016/j.jpowsour.2015.10.053 11. Sun, C., Liu, J., Gong, Y., Wilkinson, D.P., Zhang, J.: Recent advances in all-solid-state rechargeable lithium batteries. Nano Energy 33, 363–386 (2017). https://doi.org/10.1016/j. nanoen.2017.01.028

10 Future Challenges to Address the Market Demands …

293

12. Kerman, K., Luntz, A., Viswanathan, V., Chiang, Y.-M., Chen, Z.: Review—practical challenges hindering the development of solid state Li ion batteries. J. Electrochem. Soc. 164(7), A1731–A1744 (2017). https://doi.org/10.1149/2.1571707jes 13. United States Advanced Battery Consortium. Technology Transition Case Study. Retrieved from https://www.energy.gov/sites/default/files/2015/09/f26/USABC%20v8_VTO-%20U SABC%20Case%20Study%202015_01_15%20%2008-11-15%20FINAL%20CR.pdf. 1–11 (2019) 14. https://www.johnsoncontrols.com/media-center/news/press-releases/2018/11/27/johnson-con trols-and-toshiba-join-forces-on-low-voltage-lithium-ion-solutions. (2018) 15. Manthiram, A., Yu, X., Wang, S.: Lithium battery chemistries enabled by solid-state electrolytes. Nat. Rev. Mater. 2(4), 16103 (2017). https://doi.org/10.1038/natrevmats.2016.103 16. Famprikis, T., Canepa, P., Dawson, J.A., Islam, M.S., Masquelier, C.: Fundamentals of inorganic solid-state electrolytes for batteries. Nat. Mater. 18(12), 1278–1291 (2019). https://doi. org/10.1038/s41563-019-0431-3 17. Xia, S., Wu, X., Zhang, Z., Cui, Y., Liu, W.: Practical challenges and future perspectives of all-solid-state lithium-metal batteries. Chem 5(4), 753–785 (2019). https://doi.org/10.1016/j. chempr.2018.11.013 18. Varzi, A., Raccichini, R., Passerini, S., Scrosati, B.: Challenges and prospects of the role of solid electrolytes in the revitalization of lithium metal batteries. J. Mater. Chem. A 4(44), 17251–17259 (2016). https://doi.org/10.1039/C6TA07384K 19. Liu, J., Yuan, H., Liu, H., Zhao, C.-Z., Lu, Y., Cheng, X.-B., Huang, J.-Q., Zhang, Q.: Unlocking the failure mechanism of solid state lithium metal batteries. Adv. Energy Mater. 12(4), 2100748 (2022). https://doi.org/10.1002/aenm.202100748 20. Krauskopf, T., Richter, F.H., Zeier, W.G., Janek, J.: Physicochemical concepts of the lithium metal anode in solid-state batteries. Chem. Rev. 120(15), 7745–7794 (2020). https://doi.org/ 10.1021/acs.chemrev.0c00431 21. Yoshima, K., Harada, Y., Takami, N.: Thin hybrid electrolyte based on garnet-type lithiumion conductor Li7La3Zr2O12 for 12 V-class bipolar batteries. J. Power Sources 302, 283–290 (2016). https://doi.org/10.1016/j.jpowsour.2015.10.031 22. Li, Y., Gao, Z., Hu, F., Lin, X., Wei, Y., Peng, J., Yang, J., Li, Z., Huang, Y., Ding, H.: Advanced characterization techniques for interface in all-solid-state batteries. Small Methods 4(9), 2000111 (2020). https://doi.org/10.1002/smtd.202000111 23. Yamamoto, K., Iriyama, Y., Asaka, T., Hirayama, T., Fujita, H., Fisher, C.A.J., Nonaka, K., Sugita, Y., Ogumi, Z.: Dynamic visualization of the electric potential in an all-solid-state rechargeable lithium battery. Angew. Chem. Int. Ed. 49(26), 4414–4417 (2010). https://doi. org/10.1002/anie.200907319 24. Wynn, T.A., Lee, J.Z., Banerjee, A., Meng, Y.S.: In situ and operando probing of solid–solid interfaces in electrochemical devices. MRS Bull. 43(10), 768–774 (2018). https://doi.org/10. 1557/mrs.2018.235 25. Strauss, F., Kitsche, D., Ma, Y., Teo, J.H., Goonetilleke, D., Janek, J., Bianchini, M., Brezesinski, T.: Operando characterization techniques for all-solid-state lithium-ion batteries. Adv. Energy Sustain. Res. 2(6), 2100004 (2021). https://doi.org/10.1002/aesr.202100004 26. Brazier, A., Dupont, L., Dantras-Laffont, L., Kuwata, N., Kawamura, J., Tarascon, J.M.: First cross-section observation of an all solid-state lithium-ion “Nanobattery” by transmission electron microscopy. Chem. Mater. 20(6), 2352–2359 (2008). https://doi.org/10.1021/ cm7033933 27. Wang, Z., Santhanagopalan, D., Zhang, W., Wang, F., Xin, H.L., He, K., Li, J., Dudney, N., Meng: In Situ STEM-EELS observation of nanoscale interfacial phenomena in all-solid-state batteries. Nano Lett. 16(6), 3760–3767 (2016). https://doi.org/10.1021/acs.nanolett.6b01119 28. Langhus, D.L.: Modern electrochemistry, vol. 1: Ionics (Bockris, John O’M.; Reddy, Amulya K. N.). J. Chem. Educ. 76(8), 1069 (1999). https://doi.org/10.1021/ed076p1069.2 29. Mehdi, B.L., Qian, J., Nasybulin, E., Park, C., Welch, D.A., Faller, R., Mehta, H., Henderson, W.A., Xu, W., Wang, C.M., Evans, J.E., Liu, J., Zhang, J.G., Mueller, K.T., Browning, N.D.:

294

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

41.

42.

43.

44.

45.

K. P. Abhilash et al. Observation and quantification of nanoscale processes in lithium batteries by operando electrochemical (S)TEM. Nano Lett. 15(3), 2168–2173 (2015). https://doi.org/10.1021/acs.nanolett. 5b00175 Yu, C., Ganapathy, S., Eck, E.R.H.v., Wang, H., Basak, S., Li, Z., Wagemaker, M.: Accessing the bottleneck in all-solid state batteries, lithium-ion transport over the solid-electrolyte-electrode interface. Nat. Commun. 8(1), 1086 (2017). https://doi.org/10.1038/s41467-017-01187-y Yi, E., Shen, H., Heywood, S., Alvarado, J., Parkinson, D.Y., Chen, G., Sofie, S.W., Doeff, M.M.: All-solid-state batteries using rationally designed garnet electrolyte frameworks. ACS App. Energy Mater. 3(1), 170–175 (2020). https://doi.org/10.1021/acsaem.9b02101 Brissot, C., Rosso, M., Chazalviel, J.N., Lascaud, S.: Dendritic growth mechanisms in lithium/polymer cells. J. Power Sources 81–82, 925–929 (1999). https://doi.org/10.1016/ S0378-7753(98)00242-0 Harry, K.J., Hallinan, D.T., Parkinson, D.Y., MacDowell, A.A., Balsara, N.P.: Detection of subsurface structures underneath dendrites formed on cycled lithium metal electrodes. Nat. Mater. 13(1), 69–73 (2014). https://doi.org/10.1038/nmat3793 Wang, C., Fu, K., Kammampata, S.P., McOwen, D.W., Samson, A.J., Zhang, L., Hitz, G.T., Nolan, A.M., Wachsman, E.D., Mo, Y., Thangadurai, V., Hu, L.: Garnet-type solid-state electrolytes: materials, interfaces, and batteries. Chem. Rev. 120(10), 4257–4300 (2020). https:// doi.org/10.1021/acs.chemrev.9b00427 Wang, C., Yang, Y., Liu, X., Zhong, H., Xu, H., Xu, Z., Shao, H., Ding, F.: Suppression of lithium dendrite formation by using LAGP-PEO (LiTFSI) composite solid electrolyte and lithium metal anode modified by PEO (LiTFSI) in all-solid-state lithium batteries. ACS Appl. Mater. Interfaces 9(15), 13694–13702 (2017). https://doi.org/10.1021/acsami.7b00336 Cheng, E.J., Sharafi, A., Sakamoto, J.: Intergranular Li metal propagation through polycrystalline Li6.25Al0.25La3Zr2O12 ceramic electrolyte. Electrochimica Acta 223, 85–91 (2017). https://doi.org/10.1016/j.electacta.2016.12.018 Fu, C., Venturi, V., Kim, J., Ahmad, Z., Ells, A.W., Viswanathan, V., Helms, B.A.: Universal chemomechanical design rules for solid-ion conductors to prevent dendrite formation in lithium metal batteries. Nat. Mater. 19(7), 758–766 (2020). https://doi.org/10.1038/s41563-020-0655-2 Keller, M., Appetecchi, G.B., Kim, G.-T., Sharova, V., Schneider, M., Schuhmacher, J., Roters, A., Passerini, S.: Electrochemical performance of a solvent-free hybrid ceramic-polymer electrolyte based on Li7La3Zr2O12 in P(EO)15LiTFSI. J. Power Sources 353, 287–297 (2017). https://doi.org/10.1016/j.jpowsour.2017.04.014 Zhu, Y., He, X., Mo, Y.: Origin of outstanding stability in the lithium solid electrolyte materials: insights from thermodynamic analyses based on first-principles calculations. ACS Appl. Mater. Interfaces. 7(42), 23685–23693 (2015). https://doi.org/10.1021/acsami.5b07517 Chen, B., Huang, Z., Chen, X., Zhao, Y., Xu, Q., Long, P., Chen, S., Xu, X.: A new composite solid electrolyte PEO/Li10GeP2S12/SN for all-solid-state lithium battery. Electrochim. Acta 210, 905–914 (2016). https://doi.org/10.1016/j.electacta.2016.06.025 Zhu, Y., He, X., Mo, Y.: First principles study on electrochemical and chemical stability of solid electrolyte–electrode interfaces in all-solid-state Li-ion batteries. J. Mater. Chem. A 4(9), 3253–3266 (2016). https://doi.org/10.1039/C5TA08574H Xu, C., Sun, B., Gustafsson, T., Edström, K., Brandell, D., Hahlin, M.: Interface layer formation in solid polymer electrolyte lithium batteries: an XPS study. J. Mater. Chem. A 2(20), 7256– 7264 (2014). https://doi.org/10.1039/C4TA00214H Yue, L., Ma, J., Zhang, J., Zhao, J., Dong, S., Liu, Z., Cui, G., Chen, L.: All solid-state polymer electrolytes for high-performance lithium ion batteries. Energy Storage Mater. 5, 139–164 (2016). https://doi.org/10.1016/j.ensm.2016.07.003 Hu, P., Chai, J., Duan, Y., Liu, Z., Cui, G., Chen, L.: Progress in nitrile-based polymer electrolytes for high performance lithium batteries. J. Mater. Chem. A 4(26), 10070–10083 (2016). https://doi.org/10.1039/C6TA02907H Seki, S., Kobayashi, Y., Miyashiro, H., Yamanaka, A., Mita, Y., Iwahori, T.: Degradation mechanism analysis of all-solid-state lithium polymer secondary batteries by using the impedance measurement. J. Power Sources 146(1), 741–744 (2005). https://doi.org/10.1016/j.jpowsour. 2005.03.072

10 Future Challenges to Address the Market Demands …

295

46. Kim, C.-R., Tajitsu, N. & Nussey, S.: Toyota set to sell long-range, fast charging electric cars in 2022: paper. Reuters https://www.reuters.com/article/idUSKBN1AA035. (2017) 47. Lienert, P.: QuantumScape’s solid-state battery could power electric planes—director. Reuters https://www.reuters.com/article/idUSKBN28I2Y3. (2020) 48. Schnell, J., Günther, T., Knoche, T., Vieider, C., Köhler, L., Just, A., Keller, M., Passerini, S., Reinhart, G.: All-solid-state lithium-ion and lithium metal batteries—paving the way to largescale production. J. Power Sources 382, 160–175 (2018). https://doi.org/10.1016/j.jpowsour. 2018.02.062 49. Günther, T., Billot, N., Schuster, J., Schnell, J., Spingler, F.B., Gasteiger, H.A.: The manufacturing of electrodes: key process for the future success of lithium-ion batteries. Adv. Mater. Res. 1140, 304–311 (2016). https://doi.org/10.4028/www.scientific.net/AMR.1140.304 50. Fan, L.-Z., He, H., Nan, C.-W.: Tailoring inorganic–polymer composites for the mass production of solid-state batteries. Nat. Rev. Mater. 6(11), 1003–1019 (2021). https://doi.org/10.1038/ s41578-021-00320-0 51. Bates, J.B., Dudney, N.J., Neudecker, B., Ueda, A., Evans, C.D.: Thin-film lithium and lithium-ion batteries. Solid State Ion. 135(1), 33–45 (2000). https://doi.org/10.1016/S01672738(00)00327-1