Silicon carbon negative electrode material and preparation method, 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 silicon carbon negative electrode material comprises: SiO x 1. Mixing the carbon source and the dispersant to obtain the first mixed solution, x=0.5-1.0; performing the first dispersion treatment on the first mixed solution, filtering and drying to obtain the first dispersed material; performing the first carbonization on the first dispersed material processing, crushing to obtain primary particles, the particle size of the primary particles is 0.5-1 μm; mixing the primary particles with carbon source and dispersant to obtain the second mixed solution; performing the second dispersion treatment on the second mixed solution, filtering and drying to obtain The second dispersion material: performing a second carbonization treatment on the second dispersion material, pulverizing to obtain secondary particles, the particle size of the secondary particles is 10-15 μm, and obtaining a silicon carbon negative electrode material. The method of the present invention can make the finally obtained silicon-carbon negative electrode material have small volume expansion and good cycle performance.

Description

Technical field [0001] The present invention relates to the technical field of lithium ion batteries, and in particular, to a silicon carbon negative electrode material and a preparation method, a lithium ion battery. Background technique [0002] At present, the negative electrode material of the lithium ion battery is mainly graphite material, but the specific capacity of graphite materials has been close to its theoretical limit capacity (372 mAh / g), and the theoretical limit capacity of graphite materials is still small. Therefore, in order to increase the energy density of the lithium ion battery, a new type of negative electrode material is needed. The theoretical specific capacity of silicon negative material is 10 times that of graphite material, but since the silicon negative material is severely expanded after the lithium lithium, the volume expansion is 300%, which seriously affects the cycle performance of the lithium ion battery and life. [0003] At present, the s...

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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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