| abstract |
The present invention provides a battery separator which is suitable for increasing battery capacity and which can be wound with a high density, the battery separator being formed from a polyolefin microporous membrane having a width of at least 100 mm and an F25 value fluctuation range of 1 MPa or less in the width direction, and, laminated onto at least one surface of the polyolefin microporous membrane, a porous layer which has a uniform thickness and which improves electrode adhesion. The battery separator is formed from a polyolefin microporous membrane having a width of at least 100 mm and an F25 value fluctuation range of 1 MPa or less in the width direction, and, laminated onto at least one surface of the polyolefin microporous membrane, a porous layer including a fluorine-based resin and inorganic particles. (Here, the F25 value is a value obtained by applying a load to a test piece using a tensile tester, and dividing the value of the load when the test piece has elongated by 25% by the cross-sectional area of the test piece.) |