▎ 摘　　要

NOVELTY - A lithium ion battery composite separator preparing method involves adding graphene nanosheet to an aqueous solution of 4-carboxybenzenediazonium salt and hypophosphorus acid, placing in dark, washing with water and drying to obtain a modified graphene having a benzene carboxyl group covalently modified. The modified graphene is added an organic solvent and ultrasonically dispersed to obtain a modified graphene dispersion, dissolved organic polymer in organic solvent, added modified graphene dispersion liquid and pore formic acid, heated and stirred to obtain modified graphene/organic polymer blend. The modified graphene/organic polymer blend liquid is immersed in polyolefin membrane, immersed in precipitating agent and dried to obtain the finished product. USE - Method for preparing lithium ion battery composite separator. ADVANTAGE - The method enables preparing lithium ion battery composite separator with improved safety performance and electrochemical performance.