▎ 摘　　要

NOVELTY - Preparation of lithium ion battery diaphragm involves mixing 0.0001-0.01 wt.% graphene nanosheet and organic solvent to obtain less than 0.1 g/L graphene nanosheet dispersion, dissolving 1-3 wt.% polymer in organic solvent, adding resultant solution and 1-3 wt.% pore-forming agent to graphene nanosheet dispersion, heat-stirring, and treating obtained solution for 5 second to 3 hours by immersion precipitation method using coagulating bath of water, ethanol, propanol and/or glycol. USE - Preparation of diaphragm used in lithium ion battery. ADVANTAGE - The method enables preparation of diaphragm having porosity rate of 30% or more and ionic conductivity of 50% or more. The lithium ion battery using the diaphragm has decomposition voltage of 4.6 V or more and has excellent battery performance. DETAILED DESCRIPTION - Preparation of lithium ion battery diaphragm involves mixing 0.0001-0.01 wt.% graphene nanosheet and organic solvent to obtain less than 0.1 g/L graphene nanosheet dispersion, dissolving 1-3 wt.% polymer in organic solvent, adding resultant solution and 1-3 wt.% pore-forming agent to graphene nanosheet dispersion, heat-stirring, and treating obtained solution for 5 second to 3 hours by immersion precipitation method using coagulating bath of water, ethanol, propanol and/or glycol. The polymer is polyvinylidene fluoride and/or polyvinylidene fluoride-hexafluoropropylene. The organic solvent is chosen from N-dimethylacetamide, dibutyl phthalate, N-methylpyrrolidone and N,N-dimethylformamide. The thickness of the diaphragm is 5-100 mu m.