Claims

1. A flat battery comprising 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 comprise 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 a direction of the central axis,the circumferential wall of the sealing can is a single layer wall without being folded back, andthe circumferential wall of the sealing can comprises a rectilinear portion that is connected to the bottom portion via a corner portion; andthe rectilinear portion has a Vickers hardness greater than a Vickers hardness of the corner portion.

2. The flat battery according to claim 1, wherein the Vickers hardness of the corner portion is 150 or more, and the Vickers hardness of the rectilinear portion is 200 or more.

3. The flat battery according to claim 1, wherein the Vickers hardness of the rectilinear portion is 1.05 times or more greater than the Vickers hardness of the corner portion.

4. The flat battery according to claim 1, wherein the rectilinear portion is work hardened by processing that causes the rectilinear portion to be compressed.

5. The flat battery according to claim 1, wherein a gasket is pressed against the circumferential wall of the sealing can so as to press the circumferential wall of the sealing can toward the central axis.

6. The flat battery according to claim 1, wherein the circumferential wall of the sealing can is stepped at a shoulder portion, a gasket is interposed between the shoulder portion and the circumferential wall of the exterior can, and the gasket is pressed in a height direction of the sealing can.

7. A flat battery comprising 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 comprise 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 a direction of the central axis,the circumferential wall of the sealing can is a single layer wall without being folded back and is connected to the bottom portion via a corner portion;an upright portion, of the circumferential wall of the sealing can, sandwiched between the curved distal end portion of the circumferential wall of the exterior can and the bottom portion of the exterior can has a thickness greater than a thickness of the corner portion; andthe upright portion has a Vickers hardness greater than a Vickers hardness of the corner portion.

8. The flat battery according to claim 7, wherein throughout the circumferential wall of the sealing can, the Vickers hardness is greater than the Vickers hardness of the corner portion.

9. The flat battery according to claim 7, wherein the Vickers hardness of the corner portion is 150 or more, and the Vickers hardness of the upright portion is 200 or more.

10. The flat battery according to claim 7, wherein the Vickers hardness of the upright portion is 1.05 times or more greater than the Vickers hardness of the corner portion.

11. The flat battery according to claim 7, wherein the upright portion is work hardened by processing that causes the circumferential wall of the sealing can to be compressed.

12. The flat battery according to claim 7, wherein a gasket is pressed against the circumferential wall of the sealing can so as to press the circumferential wall of the sealing can toward the central axis.

13. The flat battery according to claim 7, wherein the circumferential wall of the sealing can is stepped at a shoulder portion, a gasket is interposed between the shoulder portion and the circumferential wall of the exterior can, and the gasket is pressed in a height direction of the sealing can.

14. A flat battery comprising 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 comprise 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 gasket is interposed between an outer circumferential face of the circumferential wall of the sealing can and an inner circumferential face of the circumferential wall of the exterior can;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; andin a cross-sectional shape of the sealing can in a direction of the central axis,the circumferential wall of the sealing can is a single layer wall without being folded back,the bottom portion of the sealing can is a planar portion,the circumferential wall of the sealing can comprises a rectilinear portion that is connected to the planar portion via a corner portion, andan angle θ1 formed by the planar portion and the rectilinear portion is greater than 90°.

15. The flat battery according to claim 14, wherein the angle θ1 is 90.5° or more.

16. The flat battery according to claim 14, wherein the angle θ1 is 95° or less.

17. The flat battery according to claim 14, wherein the gasket is pressed against the circumferential wall of the sealing can so as to press the circumferential wall of the sealing can toward the central axis.

18. The flat battery according to claim 14, wherein the circumferential wall of the sealing can is stepped at a shoulder portion, the gasket is interposed between the shoulder portion and the circumferential wall of the exterior can, and the gasket is pressed in a height direction of the sealing can.

19. The flat battery according to claim 14, wherein an angle θ2 formed by the planar portion and the rectilinear portion at the time when the sealing can is in a separated state before assembly is 92° or more.

20. The flat battery according to claim 14, wherein when an angle formed by the planar portion and the rectilinear portion at the time when the sealing can is in a separated state before assembly is an angle θ2, an angle difference θ3 between the angle θ2 and the angle θ1 is between 0.5° and 5° inclusive.