| 摘要 |
PROBLEM TO BE SOLVED: To provide a separator for a lithium ion secondary battery, eliminating a drawback of a nonwoven fabric separator that is not suitable for use in a lithium ion secondary battery, causing no short circuit while reduced in thickness, and excellent in electrolyte retention characteristics and rate characteristics.SOLUTION: A separator for a lithium ion secondary battery comprises a composite which comprises: a nonwoven fabric that comprises a fiber made of a thermoplastic material and having an average fiber diameter of 5-40 μm and has a basis weight of 2-20 g/m; and ultra fine fibers having 1/5-3 times in weight relative to the nonwoven fabric and having an average fiber diameter of 1 μm or less. Thermal compression treatment is performed under a condition where, when only the nonwoven fabric is subjected to the thermal compression treatment, the JIS standard (JIS Z 8741) glossiness at 60 degrees is in the range of 3-30 and the thickness is 10-40 μm, and thereby the composite has a thickness of 10-40 μm. |
