Silicon carbon composite anode material

Since silicon is a semiconductor structural material, in order to increase the diffusion rate of lithium ions in silicon electrode materials, it is necessary to improve the conductivity of silicon materials. At present, the industry has chosen mature carbon materials. Use carbon materials in different forms to composite silicon for modification, so that it forms a uniform conductive network structure, forming a silicon-carbon negative electrode material with good conductivity, good adhesion and high chemical stability....

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What is Silicon carbon composite anode material?

Since silicon is a semiconductor structural material, in order to increase the diffusion rate of lithium ions in silicon electrode materials, it is necessary to improve the conductivity of silicon materials. At present, the industry has chosen mature carbon materials. Use carbon materials in different forms to composite silicon for modification, so that it forms a uniform conductive network structure, forming a silicon-carbon negative electrode material with good conductivity, good adhesion and high chemical stability.

However, Silicon carbon composite anode material is a very difficult material to use, mainly in the following two aspects: 1. During the charging and discharging process, the volume of silicon will expand by 100%~300%, while the graphite material is only about 10%, so the expansion and contraction of the silicon-carbon negative electrode will cause the powderization of the negative electrode material, which will seriously affect the service life of the battery; 2. Silicon is a semiconductor, and its conductivity is much worse than that of graphite, resulting in a large degree of irreversibility during the lithium ion deintercalation process, thereby reducing its first coulomb efficiency, that is, there will be too much electrolyte and Li+ source, and its direct effect is also to make the battery cycle life worse.

Why do we need Silicon carbon composite anode material?

As we all know, continuously improving battery energy density is the unremitting direction of the lithium battery industry technology research institute. In the current lithium battery material system, the negative electrode material is mostly graphite material (mainly artificial graphite and natural graphite). In the battery theoretical design process, its achievable energy density has basically been fully utilized. Therefore, the current graphite negative electrode material has encountered obvious bottlenecks in improving battery energy density.

Compared with graphite negative electrode materials, silicon-based negative electrode materials have obvious advantages in energy density. The theoretical energy density of graphite is 372 mAh/g, while the theoretical energy density of silicon negative electrode exceeds it by 10 times, up to 4200 mAh/g. Therefore, the application of silicon-carbon negative electrode can increase the content of active substances in the battery, so it can greatly increase the capacity of the single battery cell. This is also an important reason why Silicon carbon composite anode material is increasingly concerned by the lithium battery field.

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