Carbon anode materials have good cycle stability and excellent electrical conductivity, and lithium ions have no obvious effect on the layer spacing. To a certain extent, they can buffer and adapt to the volume expansion of silicon, so they are often used to composite with silicon.

　　In order to learn from each other's strengths, what processes can be used to modify and optimize silicon? The composite treatment of silicon and other substances can achieve better results, and the silicon-carbon composite material is a material that has been studied more.

　　Carbon materials are currently the most widely used anode materials. Carbon materials can be divided into three types: soft carbon (graphitizable carbon), graphite, and hard carbon (amorphous carbon). The chemical equation of charge and discharge can be expressed as:

　　Carbon anode materials have good cycle stability and excellent conductivity, and lithium ions have no obvious influence on the layer spacing. To a certain extent, they can buffer and adapt to the volume expansion of silicon, so they are often used to compound with silicon.

　　Generally, composite materials can be divided into two categories according to the types of carbon materials: silicon-carbon traditional composite materials and silicon-carbon new composite materials. The traditional composite material refers to the composite of silicon and graphite, MCMB, carbon black, etc., and the new silicon-carbon composite material refers to the composite of silicon, carbon nanotubes, graphene and other new carbon nanomaterials.

　　Silicon-carbon anode materials are mainly divided into coating type, embedded type and molecular contact type according to the distribution of silicon, and divided into particle type and film type according to the form, and divided into silicon-carbon binary composite and silicon according to the type of silicon-carbon Carbon multi-composite. The following figure shows the different distribution of silicon carbon anode materials:

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

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

　　Nano-silicon particles are an earlier researched negative electrode material, but the shortcomings of its large expansion volume effect limit its application. The composite material prepared by compounding silicon-carbon has reserved expansion space for the volume expansion of silicon, and at the same time, to a certain extent, it makes up for the shortcomings of poor silicon conductivity and unstable SEI film. It has been widely used by cell manufacturers. Follow and apply. The cell anode material used in the Modle3 launched by the well-known automobile manufacturer TESLA in 2016 is the silicon-carbon anode material, which accelerates from 0 to 60 miles per hour (about 96.6 kilometers) in only 6 seconds, and has a cruising range of 215 miles (about 346 kilometers). ), those who are interested can pay attention to it.