| abstract |
To provide a separator excellent in heat resistance, shutdown function, oxidation resistance, flame retardancy and the like. A microporous film formed mainly of a thermoplastic resin and having a shutdown function, and a heat-resistant porous layer formed mainly of a heat-resistant resin and laminated on one or both sides of the microporous film. A separator for a non-aqueous secondary battery, wherein the heat-resistant porous layer contains an inorganic filler such as a metal hydroxide or a metal oxide, and the oxygen index (JIS K) of the heat-resistant porous layer -A separator for non-aqueous secondary batteries in which 7201) satisfies the following formula. 100 ≧ (oxygen index of heat-resistant porous layer) ≧ (oxygen index of heat-resistant resin) +10 [Selection figure] None |