▎ 摘　　要

NOVELTY - Preparing silicon-based cathode active material comprises (i) coating silicon dioxide containing polymer protective agent on nano silicon powder to obtain silicon/silicon dioxide composite material having nano silicon as core and silicon dioxide as shell layer, (ii) coating graphene oxide on silicon/silicon dioxide composite material to obtain silicon/silicon dioxide /graphene oxide composite material coated with silicon/silicon dioxide composite material with graphene oxide as shell layer, (iii) calcining silicon/silicon dioxide /graphene oxide composite to obtain silicon/silicon dioxide/graphene composite, and (iv) etching silicon/silicon dioxide/graphene composite with strong acid solution to obtain nano silicon as core, and sequentially coating silicon dioxide layer and graphene layer from inside to outside, silicon/silicon dioxide/graphene composite material having void between nano silicon and silicon dioxide layer and between silicon dioxide layer and graphene layer. USE - The silicon-based cathode active material is useful in lithium ion battery cathode material (claimed). ADVANTAGE - The material: not only buffer volume change of nano-silicon core during charging and discharging, but also improves electrical conductivity and mechanical toughness. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) silicon-based cathode active material comprising nano-silicon, where nano-silicon is sequentially coated with silicon dioxide layer and graphene layer from inside to outside, between nano-silicon and silicon dioxide layer and void between silicon dioxide layer and graphene layer; (2) silicon-based cathode active material obtained by above method; (3) cathode material for lithium ion battery, comprising silicon-based cathode active material, binder, and conductive agent, where binder includes polyvinylidene chloride, soluble polytetrafluoroethylene, styrene butadiene rubber, hydroxypropyl methylcellulose, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan and/or chitosan derivatives, and conductive agent is graphite, carbon black, acetylene black, graphene, carbon fiber and/or carbon nanotubes; and (4) lithium ion battery comprising silicon-based cathode active material, or lithium ion battery cathode material.