As the "heart" of electric vehicles, power batteries have attracted as much attention as the currently popular new energy vehicles. Among them, lithium-ion batteries are favored by the new energy automobile industry because of their high energy density, low self-discharge rate, high cycle efficiency, and long cycle life, and have huge market development potential. However, the current lithium-ion battery technology is not yet mature, and the problem of unstable safety still exists. In addition, the frequent accidents of battery "irregular fire" have been stimulating the nerves of consumers, and the development of solid-state battery technology may become a breakthrough. New options for electric vehicle safety issues.

　　Solid electrolytes become a trend

　　"The cost of lithium-ion batteries used now is relatively high and the technology is immature. There are many potential safety hazards in the lithium-ion batteries produced." said Wang Zhenbo, a professor at Harbin Institute of Technology.

　　According to the reporter's understanding, large power battery accidents have occurred frequently in recent years, largely due to the use of liquid electrolytes inside the batteries. "Safety is very critical for lithium-ion battery energy storage." Li Liangliang, associate professor at the School of Materials, Tsinghua University, emphasized, "Currently commercial lithium-ion batteries on the market generally use organic liquid electrolytes. Its disadvantages are that it is easy to burn and may leak. Liquid leakage causes environmental pollution.”

　　The lithium-ion battery equipment fire that occurred in Yeongam, South Korea two months ago seemed to confirm this statement.

　　"The liquid organic electrolyte currently used is flammable and explosive. Replacing the liquid electrolyte with a solid electrolyte is recognized as one of the most effective ways to improve the safety performance of lithium batteries." Associate researcher at the Qingdao Institute of Bioenergy and Processes, Chinese Academy of Sciences Dong Shanmu said.

　　Li Liangliang told reporters: "Solid electrolyte is not flammable and does not produce liquid electrolyte, so it is non-corrosive. It is an effective way to solve battery safety problems and is in line with the future battery development trend."

　　Technical bottlenecks are difficult to break through

　　"High safety is the basis and premise for the application of energy storage batteries, and solid-state is the best way to solve the safety of secondary batteries. Solid-state lithium batteries have entered the stage of accelerating global layout and research and development, and many well-known institutions are developing solid-state lithium batteries ." Wen Zhaowei said.

　　The reporter learned that many battery and automobile manufacturers, including South Korea's Samsung, Japan's Toyota and my country's CATL, have increased their investment in solid-state battery research and development, and some batteries have now entered the vehicle testing stage. Although the prospects are promising, the road to developing solid-state batteries is by no means smooth sailing due to various technical and process problems.

　　First, there is a lack of efficient electrolyte material systems. Wen Zhaowei pointed out that solid-state battery materials are currently developing rapidly, but comprehensive applications are lacking. "As the core material of solid-state batteries, there has been a breakthrough in the single indicator of solid lithium-ion conductors, but the comprehensive performance cannot yet meet the needs of large-scale energy storage." In this regard, Dong Shanmu also believes that "Today's solid-state batteries use Solid-state electrolytes generally have performance shortcomings, and there is still a big gap between the requirements of high-performance lithium-ion battery systems."

　　Secondly, the interface treatment between solid electrolyte and electrode is also a major problem currently faced by solid-state batteries. "In solid electrolytes, the transmission impedance of lithium ions is very large, and the contact area of the rigid interface with the electrode is small. Changes in the volume of the electrolyte during the charge and discharge process can easily destroy the stability of the interface." Li Liangliang pointed out. In addition, in solid-state lithium batteries, in addition to the interface between the electrolyte and the electrode, there are also complex multi-level interfaces inside the electrode. Factors such as electrochemistry and deformation will cause contact failure and affect battery performance.

　　Thirdly, unsatisfactory stability during long-term use is also a bottleneck in the development of long-life energy storage solid-state batteries. "The structure and interface of solid-state batteries will degrade over time during service, but the impact of degradation on the overall performance of the battery is still unclear, making it difficult to achieve long-term application." Wen Zhaowei said.

　　"The failure behavior of the solid battery contact interface and the failure mechanism behind it need to be clarified urgently." Dong Shanmu also said, "I believe that building high-performance solid-state batteries requires starting from two aspects. One is to build a high-performance solid-state electrolyte, and the other is to improve Interface compatibility and stability.

　　New technologies emerge one after another

　　"For solid-state batteries, we need to conduct research from the most basic materials, interfaces, and monomers to the final system modules. Only by fundamentally solving the key material and interface issues can we carry out systematic process research to meet the needs of single cells. performance requirements." Wen Zhaowei told reporters.

　　In the face of continuous challenges in the development process, various new technologies are "contesting". Reporters recently learned about some of the latest breakthroughs in solid-state battery technology.

　　For example, in terms of solid electrolyte materials, the industry has found that solid-state batteries based on the garnet-structured lithium lanthanum zirconium oxygen (LLZO) solid electrolyte system have excellent cycle performance and rate performance, and it has therefore become a major technical hotspot. "LLZO is a filler with excellent performance that can improve the performance of polymer-based composite solid-state electrolytes. Solid-state batteries based on LLZO can still maintain 81% capacity after 1,000 cycles." Li Liangliang introduced.

　　Dong Shanmu told reporters about another idea for electrolyte materials - "rigid and soft", using rigid polymer skeletons and inorganic particles to fuse with flexible polymer ion transport materials. "Through the Lewis acid-base interactions between polymers and polymers and between polymers and inorganic particles, new channels can be created for lithium ion transport and the overall performance of the electrolyte can be greatly improved."

　　The research focus on interface treatment mainly focuses on interface design and modification layers. At present, good results have been achieved in gelled interface design. Wen Zhaowei said: "The interface is modified by gel-state polymers, which not only increases the contact area but also buffers the volume effect during cycling. After 300 cycles at room temperature, there is basically no degradation. This kind of structural design is better Improved battery performance."

　　"In addition to solid-state electrolytes and interfaces, the integrated design of solid-state batteries is also very important." Li Liangliang said when talking about the future development of solid-state batteries, "Because for different fields such as energy storage and new energy vehicles, targeted battery development is required. Structural design.”

　　“In general, research on solid-state batteries is currently more academic. In terms of industrialization, some key technologies cannot be obtained because they involve the core technologies of various enterprises. As a result, technologies based on engineering applications still need to be further developed. Explore." Wen Zhaowei said.

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