Abstract text

A first object of the present invention is to provide a separator including a polyethylene microporous membrane and a heat-resistant porous layer, and that has a sufficient shutdown function and a sufficient heat resistance, and can be formed with a reduced thickness and can overcome the problem of slidability. A first aspect of the present invention is a separator for a non-aqueous secondary battery. The separator includes a microporous membrane of primarily polyethylene, and a heat-resistant porous layer of a primarily heat-resistant polymer formed on at least one surface of the microporous membrane. (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. (4) The heat-resistant porous layer has a total thickness of 3 to 12 μm.