Preparation method of silicon carbon negative pole composite material

Abstract

The invention discloses a preparation method of a silicon carbon negative pole composite material. The method comprises the following steps: dispersing silicon powder and a carbon source in a certain proportion in deionized water, stirring for some time, transferring into a teflon reaction kettle, coating the carbon precursor on the silicon powder surface by a hydrothermal process, and calcining in an inert atmosphere; dispersing the calcined material in a mixed solution a, dispersing at high speed, and drying; and carrying out etching treatment on the dried material by using an etching solution, drying the etched material to obtain the final silicon carbon negative pole composite material. The method effectively increases the lithium ion intercalation positions, improves the bulk effect of silicon, and enhances the electrochemical stability. The material has the advantages of low preparation cost and simple and controllable technique, and is suitable for large-scale industrial production.

Description

technical field [0001] The invention belongs to the field of lithium-ion battery materials, and in particular relates to a preparation method of a silicon-carbon negative electrode composite material. Background technique [0002] As a vital part of the lithium-ion battery, the energy density and cycle life of the negative electrode material have a profound impact on the overall performance of the battery. The current commercial negative electrode material still uses the traditional graphite material, but its low theoretical capacity can no longer meet the requirements. With the increasing market demand, it is urgent to find other new negative electrode materials. Silicon-based materials have attracted extensive research interest because of their high theoretical capacity and low lithium storage potential. However, silicon-based materials also have several disadvantages. Second, silicon itself is a semiconductor material with poor conductivity. These shortcomings limit the ...

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Problems solved by technology

[0002] As a vital part of the lithium-ion battery, the energy density and cycle life of the negative electrode material have a profound impact on the overall performance of the battery. The current commercial negative electrode material still uses the traditional graphite material, but its low theoretical capacity can no longer meet the requirements. The growing market demand, so it is urgent to find other new negative electrode materials

Silicon-based materials have attracted extensive research interest because of their high theoretical capacity and low lithium storage potential. However, silicon-based materials also have several disadvantages. Second, silicon itself is a semiconductor material with poor conductivity. These shortcomings limit the development of silicon materials to a certain extent.

[0003] Patent CN103022448A discloses a method for preparing a silicon-carbon negative electrode material, which is characterized in that silicon powder is first dissolved in a solvent for wet ball milling, and then natural graphite is added to it to continue ball milling to obtain the final silicon-carbon material. Powder and natural graphite are simply mixed in a physical way, without a good coating effect, the expansion problem of silicon-based materials cannot be solved, and the cycle performance of the battery is not ideal

Patent CN 102157731 A uses magnesium powder to reduce mesoporous silica at high temperature, then corrodes with hydrochloric acid to obtain porous silicon, and then coats it with liquid carbon to obtain a silicon-carbon composite material. Its porous structure can effectively relieve lithium-ion batteries. The problem of volume expansion during charging and discharging can enhance cycle stability, but the use of magnesium powder and mesoporous silica in this method will greatly increase the production cost of materials, which is not conducive to industrial production

Patent CN 102394287 A first prepares nano-precursor silicon powder through steps such as ball milling and roasting, then introduces organic carbon source gas to carry out chemical vapor deposition on the surface of silicon powder, and finally coats the obtained material in liquid phase and roasts, and the obtained silicon carbon The reversible specific capacity of the composite negative electrode material is greater than 500mAh / g, the coulombic efficiency of the first cycle is greater than 80%, and the capacity retention rate of the 50-cycle cycle is greater than 95%. In the preparation process, the chemical vapor deposition method with high cost is used, and the industrialization is difficult

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