POLYOLEFIN MICROPOROUS MEMBRANE, SEPARATOR FOR BATTERY USING THE MEMBRANE, AND BATTERY

摘要

Disclosed is a polyolefin microporous membrane comprising mainly a polyethylene resin. The membrane has (a) a shut down temperature of 135°C or lower, which is provided as a temperature at which an air permeability measured while heating the microporous membrane at a temperature rising rate of 5°C/min reaches 1 x 10⁵ sec/100 cm³, (b) an air permeability change rate of 1 x 10⁴ sec/100 cm³/°C or higher, which is provided as a gradient in a coordinate with the air permeability of 1 x 10⁴ sec/100 cm³ on a curve indicating the dependency of the air permeability on temperature, and (c) a melt-down temperature of 150°C or higher, which is provided as a temperature at which the air permeability measured while continuing the temperature rising after the temperature reaches the shut down temperature reaches 1 x 10⁵ sec/100 cm³ again.