| abstract |
And a heat-resistant porous layer provided on one side of the porous substrate, the heat-resistant porous layer including an organic binder and an inorganic filler, wherein the organic binder is a particulate polyvinylidene fluoride (Ta / Tb) of the thickness Ta of the heat-resistant porous layer and the thickness Tb of the composite film, and the heat-resistant porous layer is a porous structure in which the particulate polyvinylidene fluoride resin and the inorganic filler are connected to each other, Is not less than 0.10 and not more than 0.40, and the content of the inorganic filler in the heat-resistant porous layer is 85 mass% or more and 99 mass% or less with respect to the total mass of the organic binder and the inorganic filler, Direction is not more than 0.5 mm. |