Battery diaphragm and lithium battery prepared therefrom

A battery diaphragm, comprising:

• a porous substrate;
• and
• an adhesive layer formed on a side of the porous substrate, wherein the adhesive layer comprises a polymer material with an adhesive property, the polymer material comprises vinylidene fluoride (VDF) polymer, a raw material of the vinylidene fluoride polymer has a crystallinity in a range between 10% and 50%, the adhesive layer has a coating coefficient C, the coating coefficient C is equal to a ratio of an adhesive strength A of the adhesive layer to a value P of an increase in gas permeability per unit coating thickness of the adhesive layer, a relation C=A/P is satisfied, the coating coefficient C has a ratio in a range of 0.4<C<0.9, the adhesive strength A of the adhesive layer has a unit of N/m, the value P of the increase in the gas permeability per unit coating thickness of the adhesive layer has a unit of s/100 cc/μm, the adhesive layer is formed by coating aqueous vinylidene fluoride polymer, an α-phase in a crystalline region of the aqueous vinylidene fluoride polymer has a ratio greater than 30% and less than 70%, and the adhesive strength A of the adhesive layer is an adhesive force between the battery diaphragm and an electrode sheet.