| 摘要 |
PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery hardly causing breakage of a separator sheet and excellent in overcharge resistance.SOLUTION: The present invention provides a nonaqueous electrolyte secondary battery including a flat-shaped wound electrode body. The length of the wound electrode body in a winding axial direction is 110-200 mm, and when the length of a flat part in the direction orthogonal to a winding axis is L (mm) and the number of laminates of a separator sheet is m, 0.1≤(L/m)≤1 is satisfied. The separator sheet has an average thickness of 15-30 μm, and when the separator is heated at 150°C, a thermal shrinkage rate a(%) in the direction orthogonal to the winding axis (MD direction) and a thermal shrinkage rate b(%) in the winding axial direction (TD direction) satisfy 1≤a≤30, 0.5≤b≤10 and 1≤ab≤150. |
