POLYOLEFIN MICRO-POROUS MEMBRANE AND LITHIUM ION SECONDARY BATTERY SEPARATOR

摘要

A polyolefin microporous membrane that can realize a lithium ion secondary battery having favorable resistance against foreign matters or the like, and high cycle characteristics at a high temperature is provided. The present invention provides a polyolefin microporous membrane having a ratio of tensile strength in a length direction to that in a width direction of 0.75 to 1.25, and a thermal shrinkage rate in the width direction at 120° C. of less than 10%.