Microporous membrane and method for producing the same, battery, method for evaluating microporous membrane, method for producing microporous membrane using the same, method for producing battery, and evaluation apparatus

摘要

PROBLEM TO BE SOLVED: In a nail penetration test of a battery, which is one of battery safety tests, in particular, a separator is locally torn and an internal short circuit occurs between electrode sheets (including a current collector), and the temperature due to Joule heat generation. To provide a microporous membrane capable of suppressing a sharp rise in the temperature and a method for producing the same. SOLUTION: A rod-shaped body which extends in a rod-like shape and has a pointed tip by gradually reducing a cross section orthogonal to the length direction toward one end is formed under a predetermined condition with respect to a membrane. Piercing from the tip in the vertical direction, when a hole corresponding to the outer peripheral shape of the rod-shaped body is formed in the film, the maximum length of a crack generated in the surface direction beyond the hole is the length of the hole in the surface direction. 0% or more and 18% or less with respect to the microporous membrane.