Silicon doping and lithium supplementation are two technologies. Silicon doping of the negative electrode is to increase energy density, while lithium supplementation is to improve cycle life. Both contribute to improving the performance of power batteries and are widely used in products with high energy density.
To improve battery energy density, the specific capacity of both the cathode and anode materials needs to be increased.
The positive electrode typically uses high-nickel materials, such as the familiar 811; the negative electrode, on the other hand, uses silicon-based materials.
The reason for choosing silicon is that the theoretical specific capacity of silicon-based anode materials is 4200 Ah/g. With the current level of technology, silicon-based anodes are essential to achieve a battery capacity of 300Wh/kg.
Data shows that silicon-based anode materials are generally divided into two categories: one is silicon-carbon anode, which uses a mixture of nano-silicon and graphite, with a theoretical specific capacity of over 3000 mAh/g, but in reality just over 2000 mAh/g; the other is silicon-oxygen anode, which uses silicon suboxide mixed with graphite as the anode, with a specific capacity of approximately 1400-1800 mAh/g.
Currently, the two types of anodes have different application focuses. Lin Shaoxiong, head of anode material technology at Guoxuan High-Tech Engineering Research Institute, once said that silicon-carbon anodes are generally used more in 3C products in China; while silicon-oxygen anodes are generally used more in power batteries.
However, silicon also has significant drawbacks. It has a high expansion rate, with charge-discharge expansion reaching approximately 300%; low production volume, with only BTR currently capable of large-scale supply in China; and high cost, with data from Guosheng Securities showing that even the lowest-end silicon-based anodes cost over 100,000 yuan.
Lithium replenishment technology is also known as pre-lithiation technology. Its purpose is to compensate for lithium loss, extend cycle life, and thus slow down degradation.
The reason for lithium replenishment is mainly due to the second major drawback of silicon anode materials—low initial efficiency. Currently, lithium replenishment technology faces two major bottlenecks: safety and technological maturity.
It's worth mentioning that Tesla's 4680 battery incorporates a silicon anode; and the 210Wh/Kg LFP cell released by Guoxuan High-Tech this year also uses silicon-doped lithium supplementation technology.
