▎ 摘　　要

NOVELTY - Preparing lithium ion battery composite diaphragm comprises (1) dispersing graphene oxide in distilled water, adding dopamine and transferring it to polytetrafluoroethylene reactor, reacting at 120-140 degrees C for 2-4 hours, cooling, filtering, and drying under vacuum; (2) adding nano aluminum oxide to N,N-dimethylformamide, ultrasonically dispersing, adding polypropylene, heating to 80-90 degrees C to dissolve the polypropylene to obtain mixed solution, using casting process to obtain composite polypropylene thin film, thickness of the thin film is controlled to be 1.5-2 mm; and (3) placing the product obtained in step (1) in magnetron sputtering device, spreading the thin film obtained in the step (2) on copper plate, sputtering the product obtained in the step (1) onto thin film by magnetron sputtering, after completing sputter coating of thin film surface, using same process for sputtering coating on other side of thin film to obtain the diaphragm precursor. USE - The method is useful for preparing lithium ion battery. ADVANTAGE - The method: is simple. DESCRIPTION OF DRAWING(S) - The drawing shows a SEM picture spectrum of the composite diaphragm.