| 摘要 |
PROBLEM TO BE SOLVED: To obtain a square secondary battery in which cycle characteristics can be improved by reducing flexure of an electrode group with a simple structure.SOLUTION: A square secondary battery 1 has an electrode group 20 in which electrode plates 40, 30 are wound around a flat shaft core 10. The shaft core 10 has a substrate 11 composed of a synthetic resin material, and a stiffening member 80 composed of a material having a rigidity higher than that of the substrate 11, and extending in the winding width direction orthogonal, respectively, to the winding axis direction and the flat thickness direction of the electrode group 20 along the substrate 11. |
