Application of silicon-based negative electrode materials in lithium-ion batteries

With the vigorous development of new energy vehicles, energy storage and other markets, the market size and technical level of lithium batteries and negative electrode materials continue to improve. At present, the specific capacity of commercial graphite negative electrode materials is close to the theoretical specific capacity of graphite materials, and the commercial application of silicon-based negative electrode materials has been further accelerated.

Silicon-based negative electrode materials have become a hot spot in the research of lithium-ion battery negative electrode materials due to their extremely high theoretical specific capacity. The theoretical specific capacity of silicon negative electrode materials is much higher than that of commercial graphite negative electrode materials, and the working voltage is moderate, which makes silicon-based negative electrode materials have significant advantages in improving battery energy density. However, the volume expansion and contraction of silicon during charging and discharging is too large, resulting in material cracking and fragmentation, as well as continuous thickening of SEI film, which seriously affects the cycle stability and rate performance of the battery.

In order to solve the defects of silicon-based negative electrode materials in lithium-ion battery applications, researchers have proposed a variety of technical routes, including nanotechnology, composite material technology, structural design, surface modification, electrolyte optimization, pre-lithiation, porous silicon and alloy silicon, etc.

These technical routes cover all stages from laboratory research to industrial application, alleviating the volume expansion problem through nano-sizing and composite materials technology, improving conductivity and stability through structural design and surface modification, and enhancing the overall performance of the battery by optimizing the electrolyte system. Pre-lithiation technology can improve the initial coulombic efficiency, porous silicon structure helps to alleviate volume changes, and alloy silicon can provide higher capacity and stability. The comprehensive application of these technical routes is expected to achieve high-performance, long-life and low-cost silicon-based negative electrode materials, and promote their widespread popularity in practical applications.

At present, silicon-carbon materials and silicon-oxygen materials are the two main technical routes for silicon-based negative electrodes.

Among them, silicon-carbon negative electrode materials are known for their high first coulombic efficiency, but their cycle life needs to be improved. By realizing the nano-sizing of silicon materials, the expansion and breakage problems generated during the charging and discharging process can be reduced, thereby further enhancing their cycle life. Relatively speaking, the main advantage of silicon-oxygen negative electrode materials is their excellent cycle stability, although the first efficiency is low. However, by adopting technical means such as pre-lithiation, their first efficiency can be effectively improved.

In terms of commercial applications, currently, the main commercial applications of silicon-based negative electrode materials include carbon-coated silicon oxide, nano silicon carbon, silicon nanowires and amorphous silicon alloys. Among them, carbon-coated silicon oxide and nano silicon carbon have the highest degree of commercialization, and they are usually mixed with graphite at a ratio of 5%-10%. In recent years, silicon-based negative electrode materials are gradually being industrialized.

In the field of solid-state batteries, silicon-based negative electrode materials are considered to be one of the key development directions of solid-state battery negative electrode materials due to their high theoretical energy density, excellent fast charge and discharge performance and excellent safety performance.