How powerful is the silicon-based negative electrode? Can it replace the graphite negative electrode?

After several years of development, the range of new energy vehicles has shown a qualitative leap, but in reality, in actual use, especially long-distance travel, the range will inevitably be reduced by about 100 kilometers.

The main reason is that it is subject to the physical limit of battery capacity. For this, the solution of major manufacturers is to use high-nickel ternary lithium battery positive electrode materials to increase battery energy density to achieve the effect of increasing battery life. In the case of diversified positive electrode materials, negative electrode materials are also an important part that cannot be ignored. As one of the "three major parts" of lithium batteries, it is as important as positive electrode materials and electrolytes.

During the charging process of lithium batteries, the negative electrode acts as a carrier for lithium ions and electrons to escape from the positive electrode, and plays a role in storing and releasing energy. In the battery cost, the negative electrode material accounts for 5%-15%, which shows its importance in the lithium-ion battery system. Therefore, some manufacturers introduce silicon as a negative electrode material to improve battery life.

Among the sources of negative electrodes for power battery manufacturers, graphite negative electrodes and artificial negative electrodes are the main materials, but the current specific capacity of graphite has reached the physical limit of the material - 370mAh/g, which cannot meet the increasing endurance requirements of lithium batteries. Therefore, silicon-based negative electrode materials have become the focus, but the cost of negative electrodes using pure silicon materials is too high, more than three times that of graphite. Therefore, the mainstream solution is to use silicon oxygen and silicon carbon together with graphite, which can make the negative electrode reach a maximum specific capacity of 650mAh/g.

For example, Tesla previously mixed about 10% of silicon materials into the 2170 battery in the Model 3, which greatly improved the battery performance. Domestic companies have also strengthened the research and development of silicon negative electrode battery technology, including CATL, BYD, Guoxuan High-tech and other battery manufacturers, all of which have invested in the research and development of silicon negative electrode batteries.

Although silicon-based negative electrode material technology has gradually been mentioned by many companies, the technological progress is far less than expected. Data shows that in 2022, my country's negative electrode material shipments reached 1.37 million tons, but silicon-based materials accounted for less than 3% of the total negative electrode material shipments, which is a very small volume.

Theoretically, silicon-based negative electrodes have better performance than graphite negative electrodes, but judging from the current state of the industry, there will be no trend of large-scale use at least for now. For a long time in the future, graphite negative electrodes will still be the main negative electrode material.