Patent ID: 8906537

Claim:
A separator for a non-aqueous secondary battery, comprising: a microporous membrane of primarily polyethylene; and a heat-resistant porous layer of primarily at least one kind of heat-resistant polymer selected from the group consisting of a wholly aromatic polyamide, a polyimide, a polyamide-imide, a polysulfone, and a polyether sulfone, the heat-resistant porous layer being formed on at least one surface of the microporous membrane, the separator characterized in that: (1) the microporous membrane has a Gurley number of 25 to 35 sec/100 cc ·μm per unit thickness; (2 ) the heat-resistant porous layer contains inorganic fine particles having an average particle diameter of 0.1 to 1.0 μm; (3 ) the inorganic fine particles are 40% to 80% in volume with respect to a total volume of the heat-resistant polymer and the inorganic fine particles; and (4 ) the heat-resistant porous layer has a total thickness of 3 to 12 μm when formed on both surfaces of the microporous membrane, and a thickness of 3 to 12 μm when formed on only one surface of the microporous membrane.