Silicon-carbon negative electrode material, preparation method and lithium ion battery

Abstract

The invention provides a silicon-carbon negative electrode material, a preparation method and a lithium ion battery. The method for preparing the silicon-carbon negative electrode material comprises the steps: mixing SiOx, a carbon source and a dispersing agent to obtain first mixed solution, wherein x is equal to 0.5-1; 1.0; carrying out first dispersion treatment of the first mixed solution, andperforming filtering and drying to obtain a first dispersion material; carrying out first carbonization treatment of the first dispersion material, and performing crushing to obtain primary particleswith the particle size of 0.5-1 micron; mixing the primary particles with the carbon source and the dispersing agent to obtain second mixed solution; carrying out second dispersion treatment of the second mixed solution, and performing filtering and drying to obtain a second dispersion material; carrying out second carbonization treatment of the second dispersion material, performing crushing toobtain secondary particles with the particle size of 10-15 microns, and obtaining a silicon-carbon negative electrode material. According to the method disclosed by the invention, the finally obtainedsilicon-carbon negative electrode material has a relatively small volume expansion and a good cycle performance.

Description

technical field [0001] The invention relates to the technical field of lithium-ion batteries, in particular to a silicon-carbon negative electrode material, a preparation method, and a lithium-ion battery. Background technique [0002] At present, the negative electrode material of lithium ion battery is mainly graphite material, but the specific capacity of graphite material is already close to its theoretical limit capacity (372mAh / g), and the theoretical limit capacity of graphite material is still small. Therefore, in order to increase the energy density of lithium-ion batteries, further development of novel anode materials is required. The theoretical specific capacity of the silicon negative electrode material is 10 times that of the graphite material, but because the volume expansion of the silicon negative electrode material is serious after lithium intercalation, specifically, the volume expansion reaches 300%, which seriously affects the cycle performance and servi...

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Problems solved by technology

[0004] However, the inventors found that the above-mentioned silicon-based negative electrode materials still need to be improved in terms of improving the serious volume expansion and poor cycle performance.

Specifically, the above-mentioned silicon-based negative electrode material is a primary molding particle. If the particle size is large, the lithium ion transmission path will be lengthened, and the expansion stress of lithium intercalation will increase, making the negative electrode material easy to break and lose its activity.

If the particle size is small, the compaction density of the negative electrode sheet is low, it is difficult for the particles to disperse in the slurry, and they are easy to aggregate, which will also increase the expansion stress of lithium intercalation, making the negative electrode material easy to break and lose its activity.

In addition, the isotropy of the primary molding particles is poor, resulting in a large volume expansion of the negative electrode material during lithium intercalation, resulting in poor cycle performance

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