POROUS MEMBRANE FOR SECONDARY BATTERY, AND SECONDARY BATTERY

Disclosed is a porous membrane for a secondary battery, which has further improved output characteristics and long-term cycle characteristics when compared with conventional porous membranes. The porous membrane for a secondary battery is used for a lithium ion secondary battery or the like. Specifically disclosed is a porous membrane for a secondary battery, which contains polymer particles A that have a number average particle diameter of 0.4 µm or more but less than 10 µm and a glass transition temperature of 65°C or more and polymer particles B that have a number average particle diameter of 0.04 µm or more but less than 0.3 µm and a glass transition temperature of 15°C or less. It is preferable that the polymer particles B have a crystallization degree of 40% or less and a main chain structure that is composed of a saturated structure.