Abstract text

A flat battery of the present invention is a flat battery including an exterior can and a sealing can with which an opening of the exterior can is sealed, wherein the exterior can and the sealing can include a bottom portion and a circumferential wall extending upright from an outer circumference of the bottom portion and have a cylindrical shape that is open at one end; a distal end portion of the circumferential wall of the exterior can is bent toward a central axis of the sealing can to form a curve, whereby the exterior can is fixed to the sealing can by crimping; in a cross-sectional shape of the sealing can in the direction of the central axis, the circumferential wall of the sealing can is a single layer wall without being folded back, and the circumferential wall of the sealing can includes a rectilinear portion that is connected to the bottom portion via a corner portion; and the rectilinear portion has a Vickers hardness greater than the Vickers hardness of the corner portion.