Carbon-coated porous silicon-carbon composite material and preparation method thereof

Abstract

The invention discloses a preparation method of a carbon-coated porous silicon-carbon composite material. The method sequentially comprises the following steps: carrying out acid pickling and etchingon a silicon alloy powder, and adding carbon nanotubes before acid pickling or after etching to obtain a porous silicon mixed material; and preparing a slurry from a porous silicon mixed material, a dispersing agent and a slurry solvent, performing ball-milling dispersion or sand-milling dispersion, drying the uniformly dispersed slurry, putting the dried slurry into a high-temperature furnace, performing heat preservation carbonization in an inert gas atmosphere, and finally performing fluid energy milling to obtain a finished product. The invention also discloses a carbon-coated porous silicon-carbon composite material which is a composite material formed by uniformly coating porous silicon with carbon nanotubes. The carbon-coated porous silicon-carbon composite material disclosed by theinvention is high in conductivity, simple in preparation process, low in cost, easy to prepare on a large scale and suitable for negative electrodes of all lithium ion batteries, and expansion and shrinkage in a silicon de-intercalation lithium process are limited.

Description

technical field [0001] The invention belongs to the field of battery materials, and relates to a lithium-ion battery negative electrode material and a preparation method thereof, in particular to a carbon-coated porous silicon-carbon composite material and a preparation method thereof. Background technique [0002] Lithium-ion batteries have the advantages of high energy density, small self-discharge, wide operating voltage range, no memory effect, long service life, and no environmental pollution. They have been widely used in electronic products, electric vehicles, and energy storage fields. At present, the application of negative electrode materials is mainly based on traditional graphite materials, but the specific capacity of graphite is close to the theoretical value of 372mAh / g, and there is little room for improvement, which limits the energy density of lithium-ion batteries. Silicon-carbon composite materials have become the development trend of lithium-ion battery ...

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Problems solved by technology

[0003] However, silicon also has obvious disadvantages as the negative electrode material of lithium-ion batteries: firstly, as a semiconductor material, silicon itself has low electrical conductivity; secondly, in the process of charging and discharging, with the intercalation and extraction of lithium ions, the volume of silicon material changes greatly, resulting in material Pulverization and shedding will eventually lead to detachment from the current collector and poor cycle stability; finally, although methods such as doping and nanonization can be used to improve the electrochemical performance of silicon-based materials, these preparation methods are relatively complicated and costly , it is not easy to be prepared on a large scale, and the electrochemical performance of the prepared material needs to be further improved

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