▎ 摘　　要

NOVELTY - A negative electrode material has core-shell structure, where the core of the core-shell structure is formed by set of nano silicon, and the material for forming the shell of the core-shell structure includes graphene, the shell has an expansion space, and the expansion space is formed after the calcium carbonate is etched. USE - Negative electrode material for lithium ion battery. ADVANTAGE - The negative electrode material improves the cycle performance of the negative electrode material and the graphene superior conductivity of the coated nano-silicon, increase the conductivity of the composite material, and increases the capacity of the anode material. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for preparing negative electrode material, which involves coating the surface of nano-silicon with calcium carbonate to obtain calcium carbonate-silicon composite particles, coating the surface of the composite particles with graphene to obtain a composite material having a core-shell structure, and etching the calcium carbonate in the composite material by a hydrochloric acid solution to form an expansion space to obtain the finished product.