MICROPOROUS MEMBRANE AND PRODUCTION METHOD THEREFOR, BATTERY, MICROPOROUS MEMBRANE EVALUATION METHOD AND MICROPOROUS MEMBRANE PRODUCTION METHOD USING SAME, BATTERY PRODUCTION METHOD, AND EVALUATION DEVICE

摘要

[Problem] To provide a microporous membrane capable of suppressing an abrupt rise in temperature in a battery nail penetration test, which is a battery safety test, particularly when a separator is torn locally causing an internal short-circuit to occur between electrode sheets (including collectors) resulting in Joule heating that leads to the abrupt rise in temperature, and a production method therefor. [Solution] The microporous membrane is such that, when the distal end portion in the length direction of a rod-shaped body penetrates the membrane under predetermined conditions forming a hole in the membrane corresponding to the outer peripheral shape of the rod-shaped body, the maximum length of a crack in the surface direction emanating from the hole, relative to the length of the hole in the surface direction, is between 0% and 18% inclusive. The rod-shaped body that is used has a cross-section orthogonal to the length that successively decreases toward one end along the length of the rod to form a pointed distal end portion.