What processes can modify silicon to make lithium-ion batteries more optimized?

In order to learn from each other, what processes can be used to modify and optimize silicon? The composite treatment of silicon and other substances can play a better effect, among which the silicon-carbon composite material is a kind of material which has been studied more.

Carbon material is currently the most used negative electrode material, carbon material can be divided into soft carbon (graphitized carbon), graphite, hard carbon (amorphous carbon) three kinds, its charge and discharge chemical equation can be expressed as:

Carbon anode material has good cyclic stability and excellent electrical conductivity, and lithium ions have no obvious effect on its layer spacing, and can buffer and adapt to the volume expansion of silicon to a certain extent, so it is often used to compound with silicon.

Generally, according to the types of carbon materials, composites can be divided into two categories: silicon carbon traditional composite materials and silicon carbon new composite materials. Among them, traditional composite materials refer to silicon and graphite, MCMB, carbon black and other composites, and new silicon-carbon composite materials refer to silicon and carbon nanotubes, graphene and other new carbon nanomaterials composite.

According to the distribution mode of silicon, silicon carbon anode materials are mainly divided into coated type, embedded type and molecular contact type, and according to the morphology, they are divided into particle type and film type, and according to the number of silicon carbon types, silicon carbon binary composite and silicon carbon multiple composite. The following figure shows the different distribution of silicon carbon anode materials:

The preparation processes of silicon carbon composites include ball milling, high temperature cracking, chemical vapor deposition, sputtering deposition, evaporation and so on. The reversible capacity of the silicon carbon anode prepared by the ball milling method can reach 500~1000mAh/g, and the ball milling can promote the uniform mixing between the raw material particles and obtain a smaller particle size, and the gap between the particles is also conducive to the improvement of the cycle performance of the battery.

The high temperature cracking method is a method to obtain Si/C composite materials by cracking nano silicon particles and organic precursors or direct pyrolysis of silicone precursors. The gram capacity of silicon carbon composite materials obtained by this method is lower than that of Si/C composite materials obtained by high-energy ball milling method, but higher than that of graphite, about 300~700mAh/g. This is because the electrode material prepared by pyrolysis method contains a large number of non-electrochemically active substances, which reduces the capacity of the electrode material.

Nano-silicon particles have been studied earlier as negative electrode materials, but their large expansion volume effect limits their application. The composite material prepared by the silicon carbon composite reserves the expansion space for the volume expansion of silicon, and makes up for the shortcomings of poor conductivity of silicon and unstable SEI film to a certain extent, and has been widely concerned and applied by cell manufacturers. The famous car manufacturer TESLA launched in 2016, the Modle3 battery cell anode material is silicon carbon anode material, its speed from 0 to 60 miles per hour (about 96.6 kilometers) acceleration only 6 seconds, a range of 215 miles (about 346 kilometers), interested can pay attention to.