(Focusing
on Air-stable Sulfide)
All-solid-state
batteries, which employ solid electrolytes, are emerging as an alternative to
dramatically improve the safety of current lithium-ion batteries, whose major
drawback lies in safety concerns. The advantages of all-solid-state batteries
include excellent safety, high energy density, high output, a wide operating
temperature range, and a simple cell structure. Among the key materials of
all-solid-state batteries, solid electrolytes are of central importance, and in
terms of performance and impact within the battery, sulfide-based solid
electrolytes are currently regarded as the most advanced.
Sulfide-based
solid electrolytes exhibit high ionic conductivity (10^-3 to 10^-2 S/cm),
approaching that of liquid electrolytes, and demonstrate excellent performance
even at low temperatures. They are also characterized by superior
processability due to good interparticle adhesion. The most representative
compounds include Li₁₀GeP₂S₁₂ (LGPS),
Li₇P₃S₁₁, and Li₆PS₅Cl. Among
them, argyrodite is relatively inexpensive, well-suited for mass synthesis, and
offers good stability, which is why it is currently adopted by most
manufacturers.
As
is well known, sulfide-based electrolytes are vulnerable to moisture, and
efforts are underway to improve their ionic conductivity and stability through
doping techniques. Because interfacial reactions occur when they come into
direct contact with lithium metal and cathode materials, approaches such as
designing interfacial layers or introducing buffer layers are being explored to
stabilize the electrode interfaces. Additionally, in order to reduce the cost
of solid electrolytes, securing low-cost raw materials and mass production
process technologies is essential.
In
terms of national trends, China, which had lagged behind Korea, Japan, and the
United States in the development of all-solid-state battery technologies,
launched the China All-Solid-State Battery Industry-Academia-Research
Collaborative Innovation Platform (CASIP) in February 2024. With this
initiative, China aims to build a supply chain and advance technologies for
all-solid-state batteries, setting an ambitious goal to become the global
number one in next-generation batteries. Korea is also focusing on the
development of all-solid-state batteries and fostering the related ecosystem
through public-private battery alliance programs. In Japan, supported by the
Ministry of Economy, Trade and Industry, automotive and battery companies have
announced investments totaling as much as 1.2 trillion yen.
According
to projections by SNE Research, the global all-solid-state battery market is
expected to reach approximately 122 GWh in capacity by 2030 and about 493 GWh
by 2035, accounting for around 6.10% of all batteries. Among this, batteries
employing sulfide-based solid electrolytes are forecast to account for 45 GWh
in 2030 and 275 GWh in 2035.
Currently,
sulfide-based solid electrolytes are the most actively adopted materials for
all-solid-state batteries, but two major challenges must be overcome.
The
first is charge-discharge cycle life. To be commercialized for use in electric
vehicles, the cycle life needs to exceed several thousand cycles, whereas it
currently remains at several dozen to a few hundred cycles. The second is
reducing manufacturing costs. At present, the cost of producing all-solid-state
batteries is approximately 4 to 25 times higher per kWh than that of
conventional lithium-ion batteries, which poses a significant barrier to
commercialization.
Ultimately,
the key to commercializing all-solid-state batteries lies in developing
sulfide-based solid electrolytes and manufacturing technologies that can
achieve both long life and low cost.
This
report comprehensively describes the synthesis of sulfide-based solid
electrolytes and their application to batteries, covering the broad range of
developments to date. It also provides an in-depth discussion of air-stable
sulfide-based solid electrolytes with improved moisture resistance—a major
recent trend—and details the synthesis and application of argyrodite-type
materials in particular. Furthermore, the report extensively covers low-cost
synthesis methods for lithium sulfide (Li₂S), which serves as the precursor
material for sulfide-based solid electrolytes, along with an overview of
relevant manufacturers, their products, and their current status.
Finally,
it offers a detailed analysis of the scope of rights and examples of
implementation for patents and licensed patents filed by companies producing
lithium sulfide and sulfide-based solid electrolytes. The report also provides
an in-depth review of the most practically relevant patents related to
argyrodite and LGPS systems. We believe this content will be of significant
value to those developing or working with sulfide-based solid electrolytes.
The
strong points of this report are as follows:
① Coverage
of recent technical challenges related to solid electrolytes and their
solutions
② An
expanded scope that includes the development status of semi-solid electrolytes
and batteries incorporating them
③ Detailed
descriptions of the synthesis and characterization of lithium sulfide and
sulfide-based solid electrolytes
④ Up-to-date
trends of major manufacturers of sulfide-based solid electrolytes, along with
analysis of key patents related to LPSCl and LGPS systems
⑤ In-depth
information on the development and current status of air-stable sulfide-based
solid electrolytes, a recent hot topic
⑥ Comprehensive
listings of manufacturers producing sulfide-based solid electrolytes and
lithium sulfide
⑦ Status
updates on DOE programs and China’s CASIP initiatives related to sulfide-based
solid electrolytes
[A Chronology of Key Developments in Sulfide-Based
Composite Solid Electrolyte Membranes and Their Application to ASSBs]
[Progress of SEMCORP Within China’s CASIP Platform]
Contents
1.
Overview of Solid Electrolytes and Market Outlook
1.1
Introduction 9
1.1.1
Classification and History of Solid Electrolytes 10
1.1.2
Current Development Status of Solid Electrolytes and All-Solid-State Batteries 16
1.1.3
Key Issues of Inorganic Solid Electrolytes 18
1.1.4
Technical Challenges and Solutions Related to All-Solid-State Batteries 22
1.1.5
Semi-Solid (or Hybrid) Electrolytes and Batteries Using Them 28
1.1.6
Market Outlook by Electrolyte Type 32
1.1.7
Status of Patents and Publications Related to Solid Electrolytes 35
2.
All-Solid-State Batteries
2.1
Introduction 38
2.1.1
Polymer-Based Solid Electrolytes 39
2.1.1.1
Methods to Improve Ionic Conductivity 40
2.1.2
Inorganic Solid Electrolytes 41
2.1.2.1
Oxide-Based 41
2.1.2.2
Phosphate-Based 43
2.1.2.3
Sulfide-Based 44
2.1.2.4
Composite Solid Electrolytes 49
2.1.3
Interfaces 68
2.1.3.1
Cathode–Solid Electrolyte Interface 70
2.1.3.2
Lithium Anode–Solid Electrolyte Interface 72
2.1.3.3
Interparticle Interfaces 74
2.1.4
Technical Requirements and Future Outlook for Electrolytes 75
3.
Lithium Sulfide (Li₂S)
3.1
Introduction 77
3.1.1
Types of Solid-State Synthesis Methods 77
3.1.2
Types of Liquid-Phase Synthesis Methods 80
3.2
Li₂S Synthesis 82
3.2.1
Lab-Scale Synthesis 82
3.2.2
Industrial Production and Recycling of Li₂S 84
3.2.1.1
Industrial Production of Li₂S 84
3.2.1.2
Expected Raw Material Prices for Li₂S Manufacturing 86
4.
Sulfide-Based Solid Electrolytes
4.1
Introduction 90
4.1.1
Overview of LiPSCl (Argyrodite_LiPSX) 91
4.1.1.1
Li Argyrodite Synthesis [1]: Mechanical Milling Method 97
4.1.1.2
Li Argyrodite Synthesis [2]: Mechanical Milling + Post-Annealing Method 99
4.1.1.3
Li Argyrodite Synthesis [3]: Solid-State Sintering Method 102
4.1.1.4
Li Argyrodite Synthesis [4]: Liquid-Phase Synthesis Method 103
4.1.1.5
Application of Li Argyrodite in Batteries 109
4.1.1.5.1
Li₇₋ₓPS₆₋ₓClₓ
Composition Synthesis 109
4.1.1.5.2
AIMD Simulation 110
4.1.1.5.3
Cell Fabrication 111
4.1.1.5.4
Cell Application Results 112
4.1.1.5.5
Conclusion on Battery Application 125
4.1.2
LiPS-Based (Li₂S–P₂S₅,
etc.) 125
4.1.2.1
LiPS-Based Synthesis 127
4.1.2.2
Electrochemical Properties of LiPS 129
4.1.3
LixMPxSx (M: Ge, Sn, Si, and Al) Based 130
4.1.3.1
Synthesis Methods of LixMPxSx 132
4.1.3.2
Electrochemical Properties of LixMPxSx 133
5.
Air-Stable Sulfide-Based Solid Electrolytes
5.1
Introduction 135
5.1.1
Argyrodite Oxysulfide (LiPOCl) System [1] 135
5.1.1.1
Synthesis Methods 137
5.1.1.2
Structural Analysis 137
5.1.1.3
Application to Batteries 141
5.1.2
xLi4SnS4•(1-x)Li3PS4 System Solid Electrolytes [2] 143
5.1.2.1
Solid Electrolyte Synthesis 144
5.1.2.2
Solid Electrolyte Characterization 144
5.1.2.3
Solid Electrolyte Fabrication and Evaluation 145
5.1.2.4
Conclusion of Solid Electrolyte Evaluation 146
5.1.3
Sb-Substituted Li4SnS4 System Solid Electrolytes [3] 146
5.1.3.1
Solid Electrolyte Synthesis 148
5.1.3.2
Solid Electrolyte Structural Analysis 148
5.1.3.3
Evaluation of Air Stability of Solid Electrolytes 150
5.1.3.4
Characterization of Solid Electrolytes 151
5.1.3.5
Conclusion of Solid Electrolyte Evaluation 155
5.2
Chemical Stability of Sulfide-Based Solid Electrolytes 156
5.2.1
Overview of Chemical Stability 156
5.2.2
Chemical Stability of Sulfide-Based Solid Electrolytes 157
5.2.2.1
Chemical Stability of Sulfide Solid Electrolytes Under Humid Air 158
5.2.2.2
Chemical Stability of Sulfide Solid Electrolytes in the Presence of Solvents
and Binders 176
5.2.2.3
Compatibility With Solvents 177
5.2.2.4
Compatibility With Binders 183
5.2.3
Strategies to Improve the Chemical Stability of Sulfide-Based Solid
Electrolytes 186
5.2.3.1
Protection of Sulfide Solid Electrolytes in Humid Environments 191
5.2.3.1.1
Use of Additives 192
5.2.3.1.2
Elemental Substitution 197
5.2.3.1.2.1
Cation Dopants 197
5.2.3.1.2.2
Partial Substitution of S2- With O2- 200
5.2.3.1.2.3
Substitution With Weak Acid Groups 206
5.2.3.1.2.4
Other Elemental Substitutions 211
5.2.3.1.3
Design of New Materials 212
5.2.3.1.3.1
Li/Na‑Sn‑S (Ternary) System 213
5.2.3.1.3.2
Li/Na‑Sb‑S (Ternary) System 219
5.2.3.1.4
New Tetravalent Ion Conductors 221
5.2.3.1.5
Surface Treatment 224
5.2.3.1.5.1
Core-Shell Design 226
5.2.3.1.6
Sulfide-Polymer Composite Electrolytes 227
5.2.3.1.6.1
Summary of Air Stability Studies 229
5.2.3.1.6.2
Strategies for Improving Air Stability 230
5.2.3.2
Synthesis Methods 231
5.2.3.2.1
Selection of Solvents 232
5.2.3.2.1.1
Application of Low-Polarity Solvents 232
5.2.3.2.1.2
Application of Solvating Ionic Liquids 235
5.2.3.3
Sulfide Solid Electrolytes and Binders 237
5.2.3.4
Summary of Strategies for Improving Chemical Stability 242
5.2.3.5
Key Issues and Solutions for the Implementation of Sulfide-Based
All-Solid-State Batteries 243
6.
Key Patent Analysis and Company Status of Sulfide-Based Solid Electrolytes 246
6.1
Introduction 246
6.1.1
Overview of LiPSCl Core Patents 246
6.1.2
Trends in Patents and Academic Publications on Sulfide-Based Solid Electrolytes
247
6.1.3
Prior Patents on L-P-S-X Sulfide Electrolytes 251
6.1.4
Patent Analysis of LGPS Sulfide Electrolytes 263
6.2
Sulfide-Based Solid Electrolyte Manufacturers 267
6.2.1
Idemitsu Kosan (JP) 267
6.2.2
Mitsui Mining & Smelting (JP) 279
6.2.3
Furukawa Co., Ltd. (古河機械金属) 283
6.2.4
FUJIFILM Wako Pure Chemical Corporation 286
6.2.5
Solid Power 288
6.2.6
POSCO JK Solid Solution 295
6.2.7
Ecopro BM 300
6.2.8
Daejoo Electronic Materials 302
6.2.9
CIS 307
6.2.10
Solivis 313
6.2.11
INCHEMS 318
6.2.12
Donghwa Electrolyte 323
6.2.13
Hansol Chemical 326
6.2.14
Lotte Energy Materials 328
6.2.15
ISU Specialty Chemicals (Li2S Manufacturer) 336
6.2.16
Jeongseok Chemical (Li2S Manufacturer) 339
6.2.17
Lake Technology (Li2S Manufacturer, Global No.1) 344
6.2.18
Chunbo 348
6.2.19
Nanocamp 350
6.2.20
BEILab 352
6.2.21
Solid Ionics 356
6.2.22
ENFLOW 359
6.2.23
NEI Corp. 361
6.2.24
Albermale (US)-Universität Siegen (Ger): Li2S Manufacturer 365
6.2.25
Lorad Chemical Corp. (US): Li2S Manufacturer 368
6.2.26
AMG Lithium GmbH (Germany): Li2S Manufacturer 371
6.2.27
Stanford Advanced Materials (US): Li2S Manufacturer 373
6.2.28
Ganfeng Lithium (Li2S Manufacturer) 375
6.2.29
Hubei XinRunde Chemical (Li2S Manufacturer) 378
6.2.30
Hangzhou Kaiyada (Li2S Manufacturer) 379
6.2.31
Chengdu Hanpu High-tech Materials Co (Chengdu Hipure, Li2S Manufacturer) 380
6.2.32
Ampcera 383
6.2.33
MTI Corp. 385
6.2.34
Sulfide-Based Solid Electrolyte and All-Solid-State Battery Manufacturers in
China (Including CATL, BYD, etc.) 386
6.2.35
KERI 393
6.2.36
KETI 398
6.2.37
Summary of Sulfide-Based Solid Electrolyte and Li2S Manufacturers 403
7.
DOE National Project Programs 406
7.1 Scaling-Up & Roll-to-Roll Processing
of Sulfide Solid-State Electrolytes (PNNL) 406
7.1.1 Approach & Strategy 406
7.1.2 Summary 410
7.2 Substituted Argyrodites for All
Solid-State Batteries (SLAC National Lab., ORNL) 410
7.2.1 Objective 410
7.2.2 Experimental & Results 411
7.3 High Conductivity Thioborate Solid State
Electrolytes (Stanford Univ.) 415
7.3.1 Objective 415
7.3.2 Experimental & Results 416
8.
China’s
Industry-Academia-Research Collaborative Innovation Platform for
All-Solid-State Batteries (CASIP) 420
8.1 Development Status of All-Solid-State
Batteries by BYD 420
8.2 Development Status by SEMCORP–Central
South University 424
9.
Appendix: Manufacturing Cost Analysis of Evaluation-Grade All-Solid-State
Batteries (ASSBs) 432
9.1 Specification Design of Evaluation-Grade
ASSBs 432
9.2 Model Design of Evaluation-Grade ASSBs
433
9.3 Manufacturing Process Design of
Evaluation-Grade ASSBs 434
9.4 Cost Calculation Results for ASSB
Manufacturing 435
9.5 Technical Challenges of ASSBs 440
9.5.1 Challenges in Reducing Manufacturing
Costs 440
References 443