| 摘要 |
PROBLEM TO BE SOLVED: To provide a secondary battery separator improved in permeability of an electrolyte in a separator.SOLUTION: In a separator used as a battery separator, a fibril branch end is formed on the surface thereof. Even if the separator is folded to be used when being stored in a lithium ion secondary battery including a positive electrode 1, a negative electrode 2, a separator 3 and a nonaqueous electrolyte, the fibril branch end on the surface has a larger free space than ordinary fibrils, so that a pore route can be secured largely on a film surface, and therefor soaking properties of an electrolyte is improved and the interface resistance of a cell can be also reduced.SELECTED DRAWING: Figure 1 |
