How Is The Current Development Of Solid-state Batteries?

Solid-state batteries refer to batteries produced using solid-state electrodes and solid-state electrolytes. Different from existing liquid-form batteries, they are one of the main directions for the development of new energy vehicle batteries in the future. Recently, when the Volkswagen Group announced its second-quarter financial report, Volkswagen Group CEO Herbert Diss said that Volkswagen plans to independently produce solid-state batteries, and mass production may begin in 2024 or 2025. According to the national "Energy-saving and New Energy Vehicle Technology Roadmap", by 2025, the energy density target of lithium batteries for pure electric vehicles is 400Wh/kg, and the target in 2030 is 500Wh/kg. As far as the currently widely used ternary battery is concerned, the technical bottleneck existing at this stage makes it difficult to achieve the above goals.

If the energy density of power lithium batteries is to achieve the goal of energy density greater than 500Wh/kg as scheduled, the existing liquid electrolyte battery system may be powerless. As the next generation battery technology route for 500Wh/kg, the research and development of solid-state battery system has become a rigid demand. The medium and long-term development of the new energy automobile industry requires new technical reserves, and solid-state lithium-ion batteries are expected to become the dominant technology route for the next generation of automotive power lithium batteries. It is not only an important development direction for secondary batteries in the future, but also an important task at present.

What are the advantages of solid-state batteries compared with ternary batteries? First of all, in terms of energy density, the electrochemical window of organic electrolytes currently used in ternary and other lithium-ion batteries is limited, and it is difficult to be compatible with metal lithium anodes and newly developed high-potential cathode materials. However, solid electrolytes generally have a wider electric capacity than organic electrolytes. The chemical window helps to further increase the energy density of the battery. Secondly, in terms of volume, since the electrolyte is replaced by a solid electrolyte, the volume of a solid battery will be smaller under the same energy density. With the same amount of power, solid-state batteries will become smaller. Under the circumstance that the energy density remains the same, the mass and volume of the solid-state battery with the same charge will be smaller than that of the liquid electrolyte battery. Not only that, because there is no electrolyte in the solid-state battery, it is easier to seal it. When using it in large-scale equipment such as automobiles, it is not necessary to add additional cooling tubes, electronic controls, etc., which saves costs while reducing its own weight. After using a solid electrolyte, the graphite negative electrode can be replaced with metallic lithium, which significantly reduces the weight of the entire battery.

From the perspective of the layout of solid-state batteries in various countries, Toyota is more advanced in technology. It launched sulfide solid-state batteries in 2010. In 2014, the energy density of the battery's experimental prototype reached 400Wh/kg. As of February 2017, Toyota's solid-state battery-related patents reached 30, far higher than other companies. According to Toyota executives, Toyota will realize the industrialization of sulfide solid-state batteries in 2020. In addition, Samsung has also achieved certain results, using sulfide-based solid electrolytes to trial-produce a 2000mAh, 175Wh/kg laminated all-solid secondary battery.

Domestic company CATL is also relatively mature in sulfide solid-state batteries, and is currently accelerating the development of sulfide all-solid-state lithium metal batteries for EVs. In addition, it is worth noting that Ganfeng Lithium has recently completed the first-generation solid-state battery research and development pilot line project, and its samples have passed the inspection of the China Automobile Research Institute Automobile Inspection Center, and the project has no successful practice precedent in China, which is an international leader The technological breakthrough is expected to achieve mass production in 2019.

Compared with ternary batteries, solid-state batteries have so many advantages, why have they been unable to achieve mass production? The key to solid-state batteries is solid-state electrolyte materials. The most important reason for the difficulty in the development of solid-state batteries at this stage is the failure of electrolyte materials to achieve breakthroughs. None of the existing inorganic solid electrolyte and polymer electrolyte materials has high ionic conductivity and mechanical strength, but also has good processing properties.

The technical problems of power lithium batteries have always been the bottleneck restricting the development of new energy vehicles, and the bottleneck that solid-state batteries are difficult to break through is also in technology. In today's fierce competition in the power lithium battery industry, the companies that really have the last laugh are often those who master core technologies. Solid-state batteries are an important technology development direction in the future, and it is already the consensus of the industry. Whether Chinese companies can win the next "hard battle" still needs the joint efforts of colleagues in the industry.