Development and Research of Key Material Systems for Solid State Battery
Advanced battery technology is an important foundation for promoting equipment intelligence, energy cleanliness, and transportation electrification, and it is also a key support for realizing China's “dual-carbon” strategic goal.
I. Introduction
Advanced battery technology is an important foundation for promoting equipment intelligence, energy cleanliness, and transportation electrification, and it is also a key support for realizing China's “dual-carbon” strategic goal. At present, China has built a world-leading new energy vehicle industrial system relying on liquid lithium-ion batteries, but the existing lithium-ion batteries use flammable liquid electrolyte, which is difficult to meet the urgent needs of electric vehicles, energy storage, electric aviation, intelligent terminals, and other industries for high energy density, high safety, long life, and low-cost lithium batteries. Solid-state batteries with high specific energy, high safety and long life are globally recognized as one of the disruptive technologies to replace existing lithium-ion batteries. In recent years, the solid-state battery materials research boom has risen in academia and industry, and is regarded as the future development trend of advanced battery materials and an important way to realize high-performance next-generation batteries.
At present, major countries around the world are accelerating the layout of solid-state battery research and development and industrialization. The United States, Europe, Japan, South Korea have put forward the development plan and strategic layout related to solid-state batteries, as an important breakthrough point to strengthen their own battery technology and seize the future international battery market. Global major battery and automotive companies have released the solid-state battery product launch time, represented by solid-state batteries, new batteries are reconstructing the international battery and energy market competition pattern. China's basic research on solid-state batteries started earlier in the world, but the bottlenecks and shortcomings in key science and technology, key raw materials, process equipment and other aspects are more prominent.
In order to accelerate the development of international battery materials system to adapt to the new trends and increasingly fierce competition in the international battery market new pattern, this paper on the domestic and international solid-state battery key materials in the field of technology research and industrial development status of a comprehensive research, sorting out the domestic and international solid-state battery key materials technology system, industrial system and support system development status quo, to summarize China's solid-state battery development is facing the main problems and challenges, and targeted Put forward China's solid state battery material system self-reliance and self-improvement development strategy and related measures, in order to promote China's solid state battery key material system construction and realize the continuous development of solid state battery technology to provide reference.
II. Domestic and international solid-state battery key materials technology system
❖International solid-state battery key materials technology system development history of lithium batteries according to the different electrolytes, can be divided into liquid lithium-ion batteries, mixed solid-liquid batteries (semi-solid or quasi-solid), all-solid-state batteries 3 categories. Among them, mixed solid-liquid batteries use solid electrolyte to partially replace the liquid electrolyte; while all-solid-state batteries use solid electrolyte to replace the electrolyte, and the battery does not contain liquid at all. In general, solid-state batteries refer to hybrid solid-liquid batteries and all-solid-state batteries, and these two types of batteries are covered by the key materials technology system for solid-state batteries discussed in this study. The key materials for solid-state batteries mainly include solid-state electrolyte materials, Cathode materials, anode materials and related auxiliary materials.
1.Solid electrolyte materials
Solid electrolyte refers to lithium-ion conductors with good ion transport properties. Solid electrolytes are non-volatile, generally non-flammable, and have a wide operating temperature range and electrochemical window, so they have better safety characteristics and can be adapted to higher energy density anode and cathode material systems.
Solid-state electrolyte materials are the core components of solid-state batteries, and their progress directly affects the development process of all-solid-state batteries. According to the type of materials, solid-state electrolytes mainly include oxides, sulfides, halides, polymers and composite solid-state electrolytes (polymers + inorganic materials).
Polymer solid-state electrolytes were discovered in the 1970s and have good flexibility, film-forming properties, viscoelasticity and light weight.
In 1973, researchers revealed for the first time that poly(ethylene oxide) could form complexes when doped with alkali metal salts, and subsequently discovered that such complexes had high ionic conductivity. 1979 saw the beginning of the application of such materials to lithium metal solid-state batteries, which has since started a boom in the research of solid-state lithium polymer batteries. Later, Bollore successfully commercialized polymer solid-state batteries with an operating temperature of 80 ℃, making them the first commercially available solid-state battery type for electric vehicles. Currently, commonly used matrix materials for polymer electrolytes include polyethylene oxide, polyacrylonitrile, polymethylmethacrylate, and polyvinylidene fluoride. The development of high-voltage composite multilayer polymer solid electrolytes and room-temperature polymer electrolytes is a current research hotspot and an important goal.
Inorganic solid electrolytes have high ionic conductivity and mechanical strength. At present, according to the chemical composition, inorganic solid electrolytes mainly include oxides, sulfides, halides and so on. According to the crystal morphology, it can be divided into crystalline electrolytes and amorphous electrolytes. Among them, crystalline electrolytes mainly include chalcogenide, anticalcogenide, sodium fast ionic conductor (NASICON) type, garnet type, etc. Amorphous electrolytes mainly include amorphous oxides and amorphous sulfides, etc. Li3N is the earliest inorganic solid-state electrolyte researched, but due to the anisotropy of the conductivity and the low decomposition voltage, which limits its application in solid-state batteries. 1976, the researchers discovered NASICON type, which is the first inorganic solid-state electrolyte studied. personnel discovered a NASICON-type electrolyte, followed by the discovery of the corresponding lithium fast ionic conductor (LISICON)-type electrolyte, both of which have high ionic conductivity. At present, lithium aluminum titanium phosphate (LATP) and lithium aluminum germanium phosphate (LAGP) [(Li1+xAlxM2-x(PO4)3(M=Ti, Ge)] two solid-state electrolyte materials have been widely studied, and have good application prospects.
In 1993, LiPON (LixPOyNz) thin films were prepared by magnetron sputtering with good compatibility with lithium metal and oxide Cathodes; in the same year, Li0.34La0.5TiO3 chalcogenide-type electrolytes were discovered with room-temperature bulk ionic conductivities as high as 1.5 × 10-3 S/cm. in 2004, the researchers discovered the Gernet-structured solid-state electrolytes Li7La3Zr2O12, which has a high ionic conductivity and a wide electrochemical window.
In summary, oxide electrolytes have better chemical and thermal stability, but materials with both high ionic conductivity, wide electrochemical windows, and low-cost properties are still under development. Sulfide electrolytes have very high ionic conductivity, such as Li10GeP2S12, a sulfide discovered in 2011, which has the same level of room-temperature ionic conductivity as that of liquid electrolytes; however, sulfide electrolytes are chemically and air-stable, and are difficult to produce on a large scale and have a large interfacial impedance with the electrode material, which limits their wide application. Halide electrolytes have higher room temperature ionic conductivity and good interfacial stability with oxide Cathode, but there are shortcomings such as poor interfacial stability with lithium metal Cathode or narrower electrochemical window. Currently, the challenges commonly faced by solid-state electrolyte materials are high internal resistance and resistance in contact with the electrode interface, so the development of solid-state electrolyte materials with high conductivity and low interfacial resistance and the promotion of electrode/electrolyte interfacial modification and modification research are the key to improve the overall performance of solid-state batteries.
2.Cathode Material
Cathode material is an important factor restricting the improvement of battery energy density. Currently developed lithium batteries mainly use Cathode materials as the lithium source, and the cost accounts for approximately more than 30% of the total cost of battery materials. In addition to LiCoO2, ternary materials, LiFePO4, etc., Cathode materials commonly used in solid-state battery research, high nickel layered oxides, lithium-rich manganese-based, high-voltage nickel-manganese spinel and other materials are also under constant development.
In 1981, layered LiCoO2 was found to be used as lithium battery Cathode material, which became the first generation of commercialized lithium battery Cathode material. Subsequently, researchers have promoted the development of high-voltage resistant LiCoO2 materials through doping, coating and other modification methods. At present, lithium batteries based on LiCoO2 Cathode materials have been widely used in electronic products.
In 1983, LiMn2O4 Cathode material was discovered, which has the features of stable and excellent conductivity and lithium conductivity, good multiplicity performance, non-toxic and harmless manganese element, and low price, etc. However, the theoretical capacity of this kind of Cathode material is low, and it is currently mainly used in the field of small electric equipment such as electric bicycle.
In 1997, LiFePO4 Cathode material was discovered, which has the advantages of stable structure, good safety, good high-temperature performance, long cycle life and wide source of raw materials, and is the most widely used Cathode material in the field of power battery and energy storage battery.
In 2001, Li-Ni-Co-Mn-O ternary Cathode materials were first introduced into lithium batteries. Compared with LiCoO2, the cost of ternary materials is lower, and the ratio of Ni-Co-Mn in common ternary materials is 4:2:3, 3:3:3, 5:2:3, 6:2:2, 8:1:1, etc. With the rapid development of new energy electric vehicles, ternary materials have been widely used in lithium batteries and energy storage batteries. With the rapid development of new energy electric vehicles, ternary materials have gradually become an important Cathode material for power batteries.
3.Negative electrode materials
Negative electrode material is one of the key factors determining the performance of lithium battery, and different negative electrode materials can realize lithium storage through embedding, alloying or conversion reaction. Currently, widely used anode materials include graphite, Li4Ti5O12, amorphous carbon (hard carbon, soft carbon), silicon-based materials, lithium alloys and so on. The anode materials for solid-state batteries mainly include 3 types of carbon family anode, silicon based anode and lithium metal anode.
In 1970, researchers used lithium metal to successfully manufacture the first lithium battery, and the earliest prototype of rechargeable lithium battery was proposed in 1976. However, lithium metal in the process of charging and discharging due to large volume changes, resulting in a significant reduction in the battery cycle performance; lithium metal as a highly active material, there are obvious safety hazards, making such batteries failed to commercialize. Nevertheless, due to the lithium metal anode has a high specific capacity, low potential, low density and other advantages, solid-state lithium metal battery development is still the current battery field research hotspot.
In 1983, the Grenoble Laboratory in France for the first time in the battery to achieve the reversible embedding / de-embedding of Li + in graphite, and in 1989, Japan's Sony Corporation successfully used petroleum coke as anode materials, to achieve the commercialization of lithium-ion batteries. At present, man-made graphite with stable performance is the most important anode material for lithium-ion batteries, with excellent comprehensive performance, occupying more than 95% of the anode material market share.
Overall, relying on the first-mover advantage and early technology accumulation in lithium-ion batteries, the United States, Europe, Japan and other countries and regions dominate the original innovation and technology system of the vast majority of commercially available electrolyte materials, Cathode materials and anode materials. In the future, the development of solid-state battery technology will reshape the new pattern of the global battery technology system, therefore, countries are stepping up research and development and layout of the next generation of solid-state battery key material system.
❖China's solid-state battery key materials technology system research progress
China's basic research on solid-state batteries started earlier in the world, and the research on solid electrolytes and solid-state batteries began in the 1970s. 1978, the first report on the research of solid-state ionics; 1979, China's first laboratory of solid-state ionics in the Institute of Physics named solid-state ionics laboratory was founded, and in 1980 published the first Physics Letters LISICON article, and successfully prepared lithium zinc germanate and other fast ionic conductor materials. 1980, China's first solid-state ionics seminar was held.
In 1987, the Ministry of Science and Technology listed solid-state batteries as one of the major topics in the first batch of “National High-Tech Research and Development Program” (863 Program), and the project brought together 11 advantageous units in China to carry out collective research and provide key knowledge, technology, equipment and human resources for China's lithium battery industry. Under the support of the 863 Program, the first all-solid-state lithium battery consisting of LiV3O8 Cathode and lithium metal anode was developed in 1988. However, due to the immaturity of the battery materials and technology system at that time, there were big challenges to realize the commercialization of solid-state batteries.After 1990, the lithium-ion battery industry entered into a rapid development stage, while the progress of the research on solid-state batteries was relatively slow.In 2014, through the accumulation of sustained research and development, China's researchers were the first to put forward the in-situ solid-state technology in the international arena, by constructing multi-stage and multilayers in the battery, By constructing a multi-stage, multi-layer, multi-site continuous solid electrolyte phase in the battery, it comprehensively solves the solid-solid interface problem in solid-state batteries. 2022, high energy density solid-state batteries based on in-situ solid-state technology are the first in the world to realize large-scale mass production.
In terms of key materials and basic research on solid-state batteries, China has made a series of breakthroughs. As early as 1997, the Institute of Physics of the Chinese Academy of Sciences for the first time used “nanosilicon” as anode materials for lithium batteries, and took the lead in realizing industrialized application, which is one of the few key materials for batteries in China with completely independent intellectual property rights; and developed nanosilicon as anode materials for solid-state electrolyte-coated cathode batteries from 2014 to 2023, which is a key material for solid-state batteries. solid electrolyte-coated Cathode materials, interface pre-lithiation technology, low-expansion nano-silicon carbon anode materials, interface thermal composite and other materials and technologies were developed successively from 2014 to 2023, and the world record of energy density as high as 711 W-h-kg-1 for battery cells was created through innovative material systems and advanced process technologies. In terms of solid-state electrolyte materials, China's related research has made a series of significant progress, developed PMA/PEG-LiClO4-SiO2 composite polymer electrolyte for organic solid-state batteries, developed Li2ZrCl6 electrolyte that can be synthesized in the liquid phase, Li3Zr2Si2PO12 oxide electrolyte with high ionic conductivity and wide chemical window, and lithium ion-exchanged electrolyte that can be used for solid-state lithium-air batteries. oxide electrolytes with high ionic conductivity and a wide chemical window, lithium ion exchange zeolite membrane electrolytes for solid-state lithium-air batteries, polyether-acrylate interpenetrating network electrolytes that can be prepared by photopolymerization, and LiFePO4/Li batteries for high-temperature applications utilizing poly(propylene carbonate)-based solid-state polymer electrolytes.
In general, China has maintained a good development trend in the research of key materials and technologies for solid-state batteries, but still needs to continuously research and develop key materials for solid-state batteries to meet the performance requirements. Cathode materials will be transitioned from current ternary materials to high-nickel ternary materials and lithium-rich cathode materials, until new cathode materials with high specific capacity are required to meet the demand of solid-state batteries; anode materials will be transitioned from graphite anode to silicon-carbon anode, and finally to lithium-metal anode; solid-state electrolytes will be gradually developed from solid-liquid hybrid electrolyte and quasi-solid-state electrolyte to all-solid-state electrolyte, in which the composite solid-state electrolyte that has advantages and comprehensive advantages of polymer electrolyte and inorganic electrolyte may be able to meet the performance demand. The composite solid state electrolyte with both polymer electrolyte and inorganic electrolyte advantages and comprehensive performance may be the solid state electrolyte material that can best meet the practical application requirements in the future.
In order to ensure China's continued international leadership in the battery field, many research teams are actively carrying out basic scientific issues and key technologies of solid-state batteries, including the electrode and electrolyte key material system of solid-state batteries, solid-state batteries in the thermodynamics, dynamics, interface construction and stability, solid-state batteries, battery cell design and engineering and preparation technology, solid-state batteries, the failure mechanism of solid-state batteries, safety assessment methods and standards, and other research. Research.
III. Domestic and foreign solid-state battery key materials industry system
The global solid state battery industry is mainly distributed in China, Japan, South Korea, Europe, the United States and other countries and regions. According to incomplete statistics, as of 2023, there are approximately 53 enterprises above the size of the global layout and research and development of solid-state batteries. Japan's solid state battery industry development started the earliest, such as Japan's Toshiba Corporation in 1983 successfully developed a practical Li/TiS2 thin film solid state battery. At present, Japanese battery companies to take the mainstream technology route for solid-state batteries is sulfide solid-state electrolyte. Japan has a number of leading battery key material enterprises, such as Nichia Chemical Industry Co. and Sumitomo Metal Industries Co. in the Cathode material field, Mitsubishi Chemical Group and Resonac Group in the negative electrode material field, Asahi Kasei Group and Toray Group in the separator field, and Matsushita Electric Co. in the electric core manufacturing field. In the downstream application field of the industrial chain, Toyota Motor Corporation, Honda Giken Kogyo Co. and Nissan Motor Company are also actively involved in the production and research and development of solid-state batteries.2021, Japan established the Battery Supply Chain Association, which involves companies that can cover the entire battery industry chain, with the goal of realizing the sustainable development of Japan's battery supply chain and enhancing the competitiveness of its battery industry. In the future, Panasonic Corporation will market solid-state batteries in 2025, and automotive companies such as Toyota Motor Corporation and Honda Giken Kogyo Co. plan to realize the scale and commercial application of solid-state batteries in 2028-2030.