| 摘要 |
PROBLEM TO BE SOLVED: To provide a separator which enables the suppression of springback.SOLUTION: A separator 40 for a secondary battery comprises: a resin base material 42; and a heat-resistant layer 44 formed on the surface of the base material. The heat-resistant layer 44 includes filler and binder. In addition, when the heat-resistant layer 44 is divided in two in a direction of its thickness, an amount Rof the binder per unit volume, which is included in an area Aof the heat-resistant layer relatively closer to the base material is different from an amount Rof the binder per unit volume, which is included in an area Arelatively closer to the surface of the heat-resistant layer. The relation between the amounts Rand Ris as expressed by: R<R. According to a preferred embodiment, the heat-resistant layer 44 has an average thickness of 3-10 μm. According to another preferred embodiment, the base material 42 has an average thickness of 10-30 μm. |
