Ceramic-gel polymer multilayer composite lithium battery diaphragm and preparation method thereof

The invention discloses a preparation method of a ceramic-gel polymer multilayer composite lithium battery diaphragm. The preparation method comprises the following steps: 1, preparing aqueous PVDF (polyvinylidene fluoride) slurry and aqueous ceramic slurry; 2, thermally compounding a polypropylene diaphragm and a polyethylene diaphragm at 50-100 DEG C to obtain PP/ PE (polypropylene/ polyethylene) composite diaphragm; 3, with the PP/ PE composite diaphragm obtained in the step 2 as a coating substrate, coating the aqueous slurry prepared in the step 1 onto the PE surface of the substrate: coating the aqueous ceramic slurry to form a ceramic layer first and then coating the aqueous PVDF slurry to form a gel polymer layer, with the coating speed of 5-100m/min, and drying in a drying box with the temperature of 30-100 DEG C to obtain a final four-layer composite diaphragm. The invention further discloses a ceramic-gel polymer multilayer composite lithium battery diaphragm prepared by the preparation method. The prepared ceramic-gel polymer multilayer composite lithium battery diaphragm has the advantages of high thermal safety and high capability of keeping electrolyte.