| abstract |
A nonaqueous secondary battery separator which is a composite porous membrane obtained by integrally covering both sides of a polyolefin microporous membrane having a gas permeability (JIS P8117) of between 15 seconds/ 100 cc·μm and 50 seconds/100 cc·μm per unit thickness and a film thickness of between 5 μm and 25 μm, with a porous layer composed of polymetaphenylene isophthalamide, and which exhibits both a shutdown function and effective heat resistance for meltdown resistance, as features desired for high-energy-density, high-output, large-sized, high-performance nonaqueous secondary batteries, while also having excellent handleability and ion permeability. The film thickness of the composite porous membrane is between 6 μm and 35 μm, the gas permeability (JIS P8117) is between 1.01 and 2.00 times that of the polyolefin microporous membrane, and the polymetaphenylene isophthalamide coating amount is between 1.0 g/m 2 and 4.0 g/m 2 . |