Silicon-carbon composite material and preparation method therefor

Abstract

The invention belongs to the technical field of a silicon-carbon composite material, and specifically relates to a silicon-carbon composite material and a preparation method therefor. The silicon-carbon composite material comprises porous silicon and porous carbon at a ratio of mass parts of 4:1 to 1:4; and the silicon-carbon composite material is 3-5nm in grain diameter. The silicon-carbon composite material is prepared by the steps of mixing the porous silicon and the porous carbon based on the mass ratio, performing ball milling through a ball mill under protection of an inert gas to form a mixed material, and performing sintering and grinding on the mixed material in a carbonization furnace. The carbon-silicon composite negative electrode material prepared by the invention used for a lithium ion battery is prepared by sintering the porous carbon and the porous silicon which are prepared by adopting a special process and are used as the raw material, so that the carbon and silicon are uniform in distribution and are more tight in combination; therefore, when the composite material is used for the lithium ion battery, relatively high conductive performance and high cycling stability are achieved; and the lithium ion battery obtains high specific capability and relatively long service life.

Description

technical field [0001] The invention belongs to the technical field of silicon-carbon composite materials, and in particular relates to a silicon-carbon composite material and a preparation method thereof. Background technique [0002] As a new type of chemical power source, lithium-ion batteries have become the focus of the development of new energy materials in the world because of their high output voltage, high specific energy, long cycle life, small self-discharge, safety, no memory effect and environmental friendliness. . Electrode materials are the main factors affecting battery performance and cost. Research and development of electrode materials are of great significance to the development of lithium batteries. [0003] At present, commercial lithium-ion batteries generally use mesocarbon microspheres and modified graphite as negative electrode materials, but there are disadvantages such as low theoretical capacity (graphite is 372mAh / g), easy co-intercalation of o...

AI Technical Summary

Problems solved by technology

[0003] At present, commercial lithium-ion batteries generally use mesocarbon microspheres and modified graphite as anode materials, but there are disadvantages such as low theoretical capacity (graphite is 372mAh / g), easy co-intercalation of organic solvents, etc., which cannot meet the growing demand for high energy The demand for portable mobile power, so the research and application of high-capacity lithium-ion battery anode materials have become the key to improving battery performance

[0004] Among the known negative electrode materials for lithium-ion batteries, silicon has the highest theoretical capacity of 4200mAh / g, and a more suitable lithium-deintercalation potential (0.1-0.5Vvs.Li / Li + ), but it is easy to cause structural damage due to volume expansion during charge and discharge, and the capacity decays sharply

In order to alleviate the volume effect of silicon, researchers have modified, doped, and compounded silicon anode materials, such as Si-Ni alloy, Cu 5 Si alloy, CrSi 2 Alloys, Si-TiN composite materials, SiCN composite materials, etc., have been improved in cycle performance but are still not ideal

[0005] In recent years, researchers have carried out a series of modification studies on silicon-based negative electrode materials, including nano-silicon, coating silicon with carbon layers, and preparing silicon alloy composite materials, etc., but the cycle performance of silicon negative electrode materials has not been obtained. fundamental improvement