▎ 摘　　要

NOVELTY - Cathode active material comprises silicon core, silicon nitride layer coated on the surface of silicon core and a carbon layer coated on the surface of the silicon nitride layer, and particle size of the cathode active material is nano-grade. USE - The cathode active material is useful in cathode piece. The cathode piece is useful in battery of electric device (all claimed). ADVANTAGE - The cathode active material utilizes the combination of structure, material and particle size to alleviate the current situation of poor rate performance and low life of existing silicon-based anode active materials, and has excellent cycle stability and rate performance. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing cathode active material.