Solid-state batteries are here: The bluff or the real deal


Shi Yunyun


As one of the important development directions of power batteries, the field of solid-state batteries has been disputed. On April 8, Zhiji Motor announced at the new car launch conference: "Zhiji L6 Max Light Year version is equipped with the first generation of Light Year solid state battery, which has high safety performance, battery does not explode, high energy density, and long driving characteristics." Soon, Zhao Changjiang, general manager of Denza's sales division, bluntly said on social media: "The promotion of semi-solid vehicle batteries is playing word games." Not long ago, Zeng Yuqun, chairman and general manager of Ningde Times, also publicly proposed that there are still many problems to be overcome on the technical route of solid-state batteries, and it is still far from becoming a commodity. This makes people wonder: Has the solid-state battery achieved mass production in the end? Are the doubters really having a purely technical discussion, or are they anxious that they will be overtaken? "The solid-state battery carried by Zhiji car is actually a semi-solid-state battery. Because [the battery] still uses electrolyte, and in a normal concept, [full] solid-state batteries should not use electrolyte." Mo Ke, founder and president of true Lithium Research, said in an interview with the media that the development of solid-state battery technology is progressive and difficult to jump.


Zhiji's "solid state battery" color geometry


On April 8, Zhiji Automobile of SAIC officially released Zhiji L6 intelligent car in Shanghai, according to Liu Tao, co-CEO of Zhiji, Zhiji L6 carries 133kWh solid-state battery, CTLC (Chinese light vehicle driving condition) driving range of more than 1000km, peak charging power 400kW.


This remark immediately aroused the industry's keen attention and discussion, the focus is mainly on whether the power battery carried by Zhiji L6 is solid or semi-solid. It is reported that most of the power batteries of new energy vehicles are liquid lithium batteries, which are composed of four key elements: positive, negative, electrolyte and diaphragm, among which, electrolyte is a liquid, which facilitates lithium ions to shuttle between positive and negative electrodes, thus completing the process of charge and discharge. The essential difference between solid state batteries and the former is the shape of the electrolyte, 100% solid electrolyte is called an all-solid-state battery, and a small amount of liquid electrolyte is called a solid-liquid mixed electrolyte battery, that is, the so-called semi-solid battery.


According to product information, the battery used by Zhiji does use a solid electrolyte, but in order not to affect the transmission of lithium ions, the researchers added a "material" to the battery, that is, 10% wetting agent. As a result, the battery's electrolyte becomes a slimy "semi-solid." Therefore, as Moke said, in a strict sense, the battery carried by Zhiji L6 should be considered a semi-solid state battery. In this way, the statement of "the first mass-produced ultra-fast solid-state battery on the car" is open to question, after all, as early as December last year, the Weilai ET7 equipped with the Weilan new energy 150kWh semi-solid state battery has been tested for driving range, with a driving range of 1044km.


As the power battery supplier of Zhiji L6, Li Zheng, co-founder and general manager of Qingtao Energy, explained that unlike some previous semi-solid batteries using "jelly" electrolyte technology, the battery launched by Zhiji and Qingtao uses "high ionic conductivity, high temperature resistant solid electrolyte" and "dry solid electrolyte layer integrated forming" technology. "To enhance the lithium-ion conductivity of the solid electrolyte, we added a 10% infiltrating solution to the electrolyte." According to Li, the newly developed solid electrolyte is only 10 microns thick and uses an inorganic coating, which can reduce the possibility of short circuit of the battery cell. In addition, when the positive electrode material is heated to produce heat, this solid electrolyte layer can isolate the heat, thus ensuring the safety of the battery to the maximum. In Liu Tao's view, although the "light year" is the first generation of solid-state batteries, it has achieved more than 30% of the power with almost the same weight, and it has achieved a driving range of 1000km, which is the value of solid-state batteries instead of liquid batteries.


The relevant person in charge of Zhiji also pointed out that in fact, there is no clear standard for semi-solid state batteries and quasi-solid state batteries, and the use of solid electrolyte is definitely called solid state batteries, which is the product of two times with the use of liquid electrolyte traditional batteries.


Several difficulties remain in commercializing solid-state batteries


All along, due to the advantages of ultra-high energy density, ultra-high temperature resistance and puncture resistance, and wide temperature range working window, solid-state batteries are known as the most potential "next generation power battery", is expected to become the ultimate solution for power batteries, countries, companies are actively layout in this field. As far as the current level of technology is concerned, semi-solid battery technology is basically mature, and many products have entered the trial installation stage, such as Honeycomb energy jelly batteries and condensed matter batteries in the Ningde era belong to semi-solid batteries. However, Zhu Tao, an industry analyst at Kailian Capital, admitted that it is only a matter of time for semi-solid state batteries to be mass-produced, but there is a huge technical "gap" from semi-solid state batteries to solid state batteries.


According to Zhou Jianguang, chief technology officer and Doctor of engineering of Zhongqi Chuangzhi Technology Co., LTD., semi-solid and all-solid-state batteries are two completely different battery forms, and at present, only sulfide systems are the most promising to achieve all-solid-state batteries. However, there are also difficulties, on the one hand, the adaptation of sulfide solid electrolyte coating system is difficult to solve, on the other hand, it also faces the interface problem of sulfide cell, which needs practical solutions in the cell design, processing and application.


In addition, the development of supporting equipment for solid-state batteries and the related equipment industry chain are not mature. Zhou Jiaguang said that due to the sulfide solid electrolyte is extremely sensitive to water, the sulfide solid electrolyte preparation and application of the environment and equipment requirements are high, especially in the large-scale preparation there is no mature experience for reference, so the need for strong non-standard equipment development capability support.


Even if a technical breakthrough can be achieved, cost is another important reason to hinder the large-scale landing of solid-state batteries. Qin Lihong, president of NIO, said in the ET7 semi-solid state battery test that the cost of a 150kWh solid-state battery pack is close to a NIO ET5, that is, more than 290,000 yuan. Moke pointed out that the current challenge facing the development of semi-solid batteries is mainly how to reduce the cost to the right level. Although the technical mass production problem is not large, the cost of semi-solid batteries is still high, if only the electrolyte part is replaced by a solid state, the cost may be 30% to 40% higher than the liquid battery, or even more.


Haste makes waste. Incremental development is needed


It is true that the emergence of any new technology and products will eliminate old technology products, and once solid-state batteries achieve industrial scale in the short term, the advantages of power battery companies such as Ningde Times and BYD will also cease to exist. Based on this, Zeng Yuqun recently proposed that "Japanese automakers and other advocates of electric vehicle solid-state batteries are still several years away from commercialization, the technology is not perfect, lack of durability, and there are still safety problems", which was speculated by some people is "urgent", want to reverse the wind in public opinion. But in fact, more than one industry expert has proposed that the development of solid-state batteries should avoid "haste makes waste."


Ouyang Minggao, academician of the Chinese Academy of Sciences and vice chairman of the China Electric Vehicle 100 Association, believes that all-solid-state batteries may be industrialized before and after 2030, but in the current stage, enterprises should also be down-to-earth to solve key problems. "Now, many companies can't wait to put solid-state batteries in the car, but if you don't solve the key problems in this area, the car is just a show," he said.


Ma Xiaoli, deputy secretary-general of the China Automotive power Battery Industry Innovation Alliance, believes that before 2050, all-solid-state batteries and semi-solid-state batteries will not fully replace liquid batteries, but supplement existing liquid batteries. In the future, the three types of power batteries will go hand in hand, give play to their respective advantages for different application scenarios, and provide diversified solutions for owners.


Even Li Zheng also publicly said that Qingtao Energy's solid-state battery industrialization is divided into three steps: the first generation of solid-state batteries, which are planned to be loaded on the Zhiji car for mass production, also known as semi-solid-state batteries; The second generation of solid-state batteries will be developed in 2025; The final realization of the third generation of solid-state batteries is an all-solid-state battery. "From the first generation to the third generation, the upgrading process of the third generation of solid-state batteries is through material innovation and process equipment innovation, so that the defects of the battery are less and less, the ability to conduct ions is becoming stronger and stronger, the energy density is becoming higher and higher, and the density is gradually increasing, and the volume is becoming more and more compact." Says Li Zheng.


"Now if you do all-solid-state batteries, then from raw materials to substrate production, cell/battery packaging, battery production and application to battery recycling, the whole life cycle industry chain will cause a huge impact." Ouyang Minggao suggested that the research and development of all-solid-state batteries in China still has problems such as inconsistent understanding, dispersed strength, and uncoordinated production, university and research, and the whole industry needs to unite to establish a collaborative innovation platform, so as to jointly break through the key technologies of all-solid-state battery industrialization.


China Automotive News, April 16, 2024