| 摘要 |
PROBLEM TO BE SOLVED: To provide a square battery having high pressure-proof performance capable of surely preventing deformation of a battery case at battery internal pressure increasing time while forming the battery case in a shape causing no increase in an external shape and reduction in the inside volume. SOLUTION: In the battery case 1, four respective side plate parts 5 having a cross-sectional shape of an almost rectangular shape become respectively an outward swelling gentle circular arc shape in a prescribed radius of curvature R1, and have a cross-sectional shape of satisfying an expression of R1/r=4 to 20 on the relationship between the radius of curvature R1 and a distance r between a midpoint C2 of the respective side plate parts 5 and a central point C1 or a central point C3 of a cross-sectional surface of the battery case 1. In addition, respective corner parts of the battery case 8 are formed in a round shape having a prescribed radius of curvature R2, and have desirably a cross-sectional shape of satisfying an expression of R2/r = 0.3 to 0.8 on the relationship between the radius of curvature R2 and the distance r between the midpoint C2 of the respective side plate parts 6 and the central point C1 or the central point C3 of the cross-sectional surface of the battery case 8. |
