Solid-state batteries may replace lithium batteries and become mainstream. This technology has made many advances but has not yet been industrialized.

As the "heart" of electric vehicles, power batteries have attracted much attention. Lithium-ion batteries have been welcomed by the new energy vehicle industry and have achieved great development due to their high energy density, low self-discharge rate, high cycle efficiency, and long cycle life.

However, the current lithium-ion battery technology is not yet mature, and the problem of unstable safety still exists. The recent frequent fire incidents have raised doubts about the safety of lithium-ion batteries. Solid-state battery technology is expected to become a new option to solve the safety problem of electric vehicles.

In recent years, large-scale power battery accidents have occurred frequently, largely due to the use of liquid electrolytes inside the batteries. Commercial lithium-ion batteries generally use organic liquid electrolytes, which are flammable and may leak liquid, causing environmental pollution. Solid electrolytes are non-flammable and do not produce liquid electrolytes, so they are non-corrosive. Replacing liquid electrolytes with solid electrolytes is recognized as one of the most effective ways to improve the safety performance of lithium batteries.

Solid-state lithium batteries have entered a stage of accelerated global deployment and research and development, and many well-known institutions are developing solid-state lithium batteries. Many battery and automobile manufacturers, including Samsung in South Korea, Toyota in Japan, and CATL in my country, have increased their investment in solid-state battery research and development, and some batteries have entered the stage of vehicle installation and testing. Although the prospects are promising, the road to developing solid-state batteries is by no means smooth due to various technical and process problems.

The solid electrolytes used in today's solid-state batteries generally have performance shortcomings, and there is still a big gap from the requirements of high-performance lithium-ion battery systems. The interface treatment between solid electrolytes and electrodes is also a major problem currently facing solid-state batteries. In solid electrolytes, the lithium ion transmission impedance is very large, and the rigid interface contact area with the electrode is small. The change in electrolyte volume during charging and discharging can easily destroy the stability of the interface.

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 can cause contact failure and affect battery performance.

Poor stability during long-term use is also a bottleneck in the development of long-life solid-state batteries for energy storage. The structure and interface of solid-state batteries will degrade over time during service, but the mechanism of how degradation affects the overall performance of the battery is still unclear, making it difficult to achieve long-term application.

Only by fundamentally solving the key material and interface problems can we carry out systematic process research to meet the performance requirements of single cells. At present, various new technologies are "a hundred schools of thought contending", and some solid-state battery technologies have made the latest breakthroughs.

In terms of solid electrolyte materials, the industry has found that solid-state batteries based on garnet-structured lithium lanthanum zirconium oxide (LLZO) solid electrolyte systems have excellent cycle performance and rate performance, which has become a major technical hotspot. LLZO is an excellent filler that can improve the performance of polymer-based composite solid electrolytes. After 1,000 cycles, the capacity of LLZO-based solid-state batteries can still be maintained at 81%.

Another electrolyte material idea is to use a rigid polymer skeleton and inorganic particles to fuse with a flexible polymer ion transport material. Through the Lewis acid-base interaction between polymers and between polymers and inorganic particles, new channels can be created for lithium ion transport, greatly improving the overall performance of the electrolyte.

The research hotspots of interface treatment are mainly focused on interface design and modification layer. At present, the gel interface design has achieved good results. The interface is modified by gel polymer, which increases the contact area and can also buffer the volume effect during the cycle. After 300 cycles at room temperature, there is basically no degradation. Such structural design has improved the battery performance.

In general, the research on solid-state batteries is still more academic. In terms of industrialization, some key technologies involve the core technologies of various companies and cannot be obtained, resulting in the need for further exploration of technologies based on engineering applications.

As a winner of Toutiao's Qingyun Plan and Baijiahao's Bai+ Plan, the 2019 Baidu Digital Author of the Year, the Baijiahao's Most Popular Author in the Technology Field, the 2019 Sogou Technology and Culture Author, and the 2021 Baijiahao Quarterly Influential Creator, he has won many awards, including the 2013 Sohu Best Industry Media Person, the 2015 China New Media Entrepreneurship Competition Beijing Third Place, the 2015 Guangmang Experience Award, the 2015 China New Media Entrepreneurship Competition Finals Third Place, and the 2018 Baidu Dynamic Annual Powerful Celebrity.