Abstract: This embodiment includes an electrode assembly; a case for housing the electrode assembly; and an external terminal made of a metal and disposed on the case, in which the external terminal includes: a flange extending along an outer surface of the case; and a shaft extending from the flange to pass through the case and be conductive with the electrode assembly, the flange is made of a clad material having a plurality of metal layers layered in a passing direction of the shaft, each adjacent ones of the plurality of metal layers are made of different metals in kind, and one of the plurality of metal layers of the flange at one end in the passing direction is made of the same metal in kind as the metal of the shaft, and is welded to the shaft.