▎ 摘　　要

NOVELTY - Preparation of porous spherical graphene-coated silicon negative electrode composite material involves (i) preparing graphene oxide aqueous dispersion, (ii) ultrasonically-dispersing nanosilicon in the graphene oxide aqueous dispersion to obtain a graphene oxide-nanosilicon dispersion, and (iii) adding nitric acid solution to the graphene oxide-nanosilicon dispersion liquid, ultrasonically-mixing, hydrothermally-reacting at 120-250 degrees C for 6-48 hours in a protective atmosphere, and calcining at 300-1000 degrees C for 0.5-12 hours. USE - Preparation of porous spherical graphene-coated silicon composite material used for forming negative electrode for lithium ion battery (all claimed). ADVANTAGE - The negative electrode formed using the porous spherical graphene-coated silicon composite material provides lithium ion battery having improved capacity and cycle characteristics at large rates. The nanosilicon can significantly reduce its absolute volume change during reversible charging/discharging process, improve utilization rate of silicon material, and wrap spherical graphene which can effectively buffer huge volume effect of silicon. The activation of graphene by nitric acid solution causes a lot of pores to be distributed on its surface, which provides a shortcut for lithium ions and reduces its diffusion path during charging/discharging process.