Patent ID: 8481201

Claim:
A case of a secondary battery, comprising: opposing first and second main walls; opposing first and second side walls extending between the main walls, and having a smaller surface area than the main walls; and a bottom wall connected to ends of the main walls and the side walls, the bottom wall having: an inner surface facing an opening of the case and an opposing outer surface; edge portions connected to the side walls; a central portion disposed between the edge portions, having a thickness that is less than the thicknesses of the edge portions; and a first notch disposed in the central portion, extending from the first main wall to the second main wall wherein the first notch is dimensioned and positioned in the central portion so that the bottom wall opens to the outside under a longitudinal compression environment and wherein the thickness of the bottom wall gradually decreases from the side walls to a point in the central portion that is equidistant to the side walls.