Preparation method of silicon carbon lithium ion battery cathode material

Abstract

The invention provides a preparation method of a silicon carbon lithium ion battery cathode material, which comprises the following steps: a) mixing a polymer solution, silicon powder and graphite to obtain a mixed solution; b) performing freeze drying of the mixed solution to obtain a solid mixture; c) sintering the solid mixture to obtain the silicon carbon lithium ion battery cathode material. The invention adopts freeze drying instead of a common drying method; the freeze drying means freezing the material, allowing the solvent component to rapidly become a solid state and to directly sublime under a vacuum condition so as to reach the drying purpose. With the process, the composite material and a carbon source can rapid coagulate within a short period, which avoids the problems of surface oxidation of the silicon material caused by normal temperature drying or high temperature drying, and non-uniform coating caused by settlement of the composite material powder. The obtained carbon-coated material has improved recycle performance and capacity when compared with materials obtained by common drying.

Description

technical field [0001] The invention relates to the field of preparation methods of electrode materials, in particular to a preparation method of a negative electrode material for a silicon-carbon lithium ion battery. Background technique [0002] In the field of lithium-ion battery anode materials, the mainstream anode material is graphite, and its theoretical capacity is only 372mAh / g, which greatly limits the capacity performance of lithium-ion batteries. In order to further improve the reversible capacity of anode materials, it is necessary to explore and develop new anode materials. Among them, Si has attracted extensive attention of researchers due to its incomparable capacity advantage (theoretical specific capacity is 4200mAh / g) compared with other materials. However, the biggest problem with Si is that the huge volume change in the process of lithium insertion and extraction causes the pulverization of the material, resulting in the instability of the electrode str...

AI Technical Summary

Problems solved by technology

This type of coating method is simple to operate and the process is easy to control. However, in the process of solvent volatilization and drying, the sedimentation of silicon particles will inevitably occur, which will cause the particles of the composite material to not be evenly distributed in the organic carbon source, resulting in carbon coating. Inhomogeneous coverage affects the electrochemical performance of the entire composite

[0005] Chinese patent CN101710617A discloses that Dalian Lichang New Materials Co., Ltd. uses pitch as a pyrolytic carbon source to coat silicon and graphite powder with pyrolytic carbon, and uses traditional drying methods to dry the carbon-coated silicon and graphite powder, and After spray granulation, high magnetic carbonization and other processes, the specific capacity of the obtained silicon-carbon material is 1000mAh / g, and the cycle performance is good. However, in order to uniformly coat the material with pitch, this method uses nano-processing of mesophase pitch and uses Spray injection and other devices, the process flow is complicated, and the operation cost is high

Chinese patent CN101339987A discloses that Changsha Hairong Electronic Materials Co., Ltd. uses silicon and graphite for high-energy ball milling, and then ball mills with asphalt to prepare silicon carbon materials. The simple traditional drying method still affects the performance of the material.

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