Patent ID: 7563536

Claim:
A prismatic sealed secondary battery, comprising: an electrode assembly including a positive electrode, and a negative electrode, and a separator sandwiched between the positive electrode and the negative electrode; a case which is made of a metal material formed in one or more plates, has a prismatic tubular shape with four lateral planes, one open end, and one closed end, and has an internal space in which the electrode assembly is housed, the four lateral planes, each of which has a plate thickness, being composed of two main planes and two secondary planes, the main planes being laid along a direction intersecting thickness of the positive electrode or the negative electrode; and a sealing cap joined with the open end to seal the internal space, wherein on an area on at least one of the main planes, one or more linear heat strain signatures formed as a result of an application of heat are created, the area being apart from outer lines of the at least one of the main planes, linear portion formed within each of the linear heat strain signatures is, on cross section, fanned out inwardly toward the plate thickness from a center of a width of the linear heat strain signature, and is composed of a recrystallized structure, and one or more depressions are formed, surrounding the linear heat strain signatures.