HERMETICALLY SEALED BATTERY
To provide a hermetically sealed battery having a seal that also serves as a terminal plate, in which the seal can be reliably welded to a battery case without causing spatters and the like while ensuring good weld strength of a lead to the seal. A seal 17 is constituted by an aluminum layer 25 that is made of aluminum or the like and is disposed on a battery case 6 side and a dissimilar metal layer 26 having less thermal conductivity than the aluminum layer 25 and is formed on the aluminum layer 25. The aluminum layer 25 has a larger size than the dissimilar metal layer 26, and an outer peripheral edge portion 25 a of the aluminum layer 25 protrudes outward beyond an outer peripheral edge 26 a of the dissimilar metal layer 26. The seal 17 is welded to the battery case 6 in a state where the central axis S of a laser beam 27 moves along an outer peripheral edge 25 b of the aluminum layer 25 and an edge 29 a of a welding mark 29 due to irradiation with the laser beam 27 on the dissimilar metal layer 26 side is positioned outside the outer peripheral edge 26 a of the dissimilar metal layer 26.
1 . A hermetically sealed battery comprising a battery case at least the exterior side of which is formed of aluminum or an aluminum alloy and a seal that seals a liquid injection hole that is formed in the battery case and used to inject an electrolyte solution, the seal being welded to a portion around the liquid injection hole in the battery case by a laser beam,
wherein the seal is constituted by an aluminum layer that is made of aluminum or an aluminum alloy and is disposed on the battery case side and a dissimilar metal layer that is made of a metal or a metal alloy having less thermal conductivity than the aluminum layer and is formed on the aluminum layer;
the aluminum layer has a larger size than the dissimilar metal layer, and an outer peripheral edge portion of the aluminum layer protrudes outward beyond an outer peripheral edge of the dissimilar metal layer; and
the seal is welded to the battery case in a state where an edge of a welding mark due to irradiation with the laser beam on the dissimilar metal layer side is positioned outside the outer peripheral edge of the dissimilar metal layer.
2 . The hermetically sealed battery according to claim 1 , wherein the seal is welded in a state where a central axis of the laser beam coincides with an outer peripheral edge of the aluminum layer.
3 . The hermetically sealed battery according to claim 1 , wherein the seal has a shaft section that is formed integrally with the aluminum layer and that projects downward from a lower surface of the aluminum layer, the shaft section being inserted into the liquid injection hole.
4 . The hermetically sealed battery according to claim 1 , wherein the position of the edge of the welding mark on the dissimilar metal layer side is an average of 0.1 mm or more to the outside of the position of the outer peripheral edge of the dissimilar metal layer.
5 . The hermetically sealed battery according to claim 1 , wherein the position of the edge of the welding mark on the dissimilar metal layer side is 1 mm or less from the position of the outer peripheral edge of the dissimilar metal layer.
6 . The hermetically sealed battery according to claim 1 , wherein the outer peripheral edge portion of the aluminum layer protrudes outward beyond the outer peripheral edge of the dissimilar metal layer by 0.1 mm or more.