| abstract |
A secondary battery includes: a housing member having a bent portion defining an open end; a battery element including a positive electrode, a negative electrode, and an electrolyte, and being housed in the housing member; The housing member extends in a cross direction intersecting the housing direction so as to close the open end of the housing member, and has a lower surface opposed to the battery element, an upper surface on the opposite side of the lower surface, and a lower surface and an upper surface respectively connected to the lower surface. a side surface; and a sealing member interposed between the bent portion and the cover member. The bent portion is bent along the lower surface, side surface, and upper surface of the cover member, respectively, and includes a specific bent portion bent along the side surface and the upper surface of the cover member, respectively. The bending ratio R1 (=(L1/D1) calculated based on the outer diameter D1 (mm) of the housing member defined by the bending portion in the intersecting direction, and the bending length L1 (mm) of the specific bending portion in the intersecting direction )×100) is 10% or more and 13% or less. |