A SILICON-CARBON COMPOSITE NEGATIVE MATERIAL FOR LITHIUM ION BATTERY AND THE PREPARATION METHOD OF THE SAME

摘要

A silicon-carbon composite negative material for lithium ion battery and the preparation method of the same of which the technical problem to be solved is to improve the specific capacity of the battery. The material of the invention is based on the composite particles of silicon-phase particles and carbon-phase particles which are spheric or quasi-spheric and coated with carbon coating layer. The preparation is as following: crushing the silicon-phase particles; mixing and coating the composite particles, obtained by mixing the silion-phase particles and the carbon-phase particles, with the precursor of pyrolytic carbon of organic matter; carbonizing treatment; and crashing and breaking. Comparing with prior art, the reversible specific capacity of the composite negative electrode material which is coated with coating layer and based on the composite material of the silicon-phase particles and the carbon-phase particles is larger than 450mAh /g, the coulomb efficiency higher than 85% at first cycle, the conservation rate for capacity is larger than 80% in 200 times of circulation. The volume effect of the silicon-containing active material during the intercalation and de-intercalation process can be decreased, the diffusion action of the lithium in the active material is improved, and the material obtained can be used as negative electrode material for lithium ion battery suitably in the application of the portable device and electric tools.