| 摘要 |
PROBLEM TO BE SOLVED: To improve the performance of a lithium ion secondary battery having a separator including a heat-resistant layer.SOLUTION: A lithium ion secondary battery 10 proposed herein comprises an electrode assembly 40, and a battery case 20 housing the electrode assembly. The electrode assembly 40 includes a LiBOB-derived coating film and Na. A set of separators 72 and 74 each have a base material 76 comprising a plastic porous film, and a heat-resistant layer 78 formed on a surface of the base material 76 and comprising a filler and a binder. The binder of the heat-resistant layer 78 has a binder group A consisting of binders having softening temperatures of 175°C or higher, and a binder group B consisting of binders having softening temperatures of 175°C or lower. The binders of the binder group B have an average molecular weight of 10,000-500,000. Supposing that the weight of the binder group A is 100, the weight of the binder group B is 5 or more and 50 or less. |
