According to recent media reports, Zhiyi Auto is jointly developing "silicon-doped lithium-ion battery cell" technology with CATL. The two parties will share technology patents, collaborate on various rigorous vehicle tests, and mass-produce batteries using this technology in the future.
It has been revealed that batteries based on "silicon-doped lithium-ion cells" technology will have an energy density 30%-40% higher than the current industry-leading level. Within the new architecture of Zhiji Auto, they can achieve a maximum range of approximately 1,000 km and zero degradation over 200,000 km.
So, what is the "silicon-doped lithium-ion battery cell" technology?
It is understood that 811 batteries need to be used with silicon-carbon and silicon-oxygen batteries, but SiOx has a low initial efficiency, which requires a lithium replenishment process to achieve.
As the demand for driving range in new energy vehicles continues to increase in practical applications, power battery materials are also developing towards providing higher energy density. Traditional graphite anodes for lithium-ion batteries can no longer meet current needs, and high-energy-density anode materials (silicon-carbon, silicon-oxygen) have become a new hot topic for companies.
Under ideal conditions, pure Si can achieve a specific capacity of 4200 mAh/g when fully lithium-intercalated, but this is accompanied by a volume expansion of up to 300%. Another silicon oxide, SiOX, is used as an anode material. The bond energy of the Si-O bond is twice that of the Si-Si bond. Since lithium oxide LiXO is generated during the first lithium intercalation of SiOx, the initial coulombic efficiency of the silicon suboxide material is only about 70%.
Despite numerous technological improvements in recent years, the initial efficiency has only increased to around 80%, which is still far behind the 94% efficiency of graphite materials. In order to narrow this gap, various research institutes, universities, and companies have proposed their own material modification methods to enable SiOX materials to fully utilize their high specific capacity advantage.
The lithium replenishment process for silicon-carbon anode involves pre-coating a layer of lithium metal onto the surface of the silicon-carbon anode. This coating is in close contact with the anode and reacts with the anode after electrolyte is injected, embedding itself into the anode particles. This pre-stores a portion of lithium ions inside the anode, thereby compensating for the Li ions consumed during the first charge-discharge or cycle process due to the formation or repair of the SEI film.
Compared to the high-difficulty and high-investment negative electrode lithium replenishment process, positive electrode lithium replenishment is much simpler. The typical positive electrode lithium replenishment process involves adding a small amount of high-capacity positive electrode material during the positive electrode homogenization process. During the charging process, excess Li elements are extracted from these lithium-rich positive electrode materials and embedded into the negative electrode to replenish the irreversible capacity of the first charge and discharge.
It is still unclear which technology CATL's 811 battery will use, but it is basically a foregone conclusion that Zhiji Auto will use the most advanced lithium battery.
