▎ 摘　　要

NOVELTY - A composite diaphragm comprises a base film, a graphene oxide layer provided on one side of the base film, a polyaniline layer arranged on the side of graphene oxide layer away from the base film, and a polymethylmethacrylate layer arranged on one side of the base film away from the graphene oxide layer. USE - Composite diaphragm of lithium ion battery (claimed). ADVANTAGE - The composite diaphragm provides battery having large battery capacity, good cycle performance and safety performance. The electrolyte has large angle contact good permeability to lithium ion, and excellent wetting property. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of the composite diaphragm, which involves (A) stirring and mixing graphene oxide and polyacrylic acid, and coating on side of the base film to form a graphene oxide layer to obtain a diaphragm (I), (B) dissolving aniline in a solvent and adding acid for doping to obtain a solution (I), (C) dissolving ammonium persulfate in a solvent to obtain an initiator solution, and mixing and stirring the solution (I) and the initiator solution to obtain a solution (II), (D) immersing the graphene oxide side of diaphragm (I) in solution (II) to form a polyaniline layer and refrigerating to form a diaphragm (II), (E) coating polymethylmethacrylate solution on diaphragm (II) on the side of base film away from the graphene oxide layer to form a polymethylmethacrylate layer.