Cylindrical sealed battery and battery pack

A cylindrical sealed battery comprising:

• a bottomed cylindrical exterior case, a sealing member, a cylindrical wound electrode assembly including a positive electrode plate and a negative electrode plate wound together via a separator, and an electrolyte,
• the cylindrical wound electrode assembly and the electrolyte being accommodated in the exterior case, an open end of the exterior case being crimped together with the sealing member via an insulating gasket so as to form a seal,
• the sealing member including a lid having a thin and fragile portion, an insulating ring disposed on an inner side of the lid, and a terminal plate having a thin and fragile portion disposed on the inner side of the lid,
• the terminal plate being electrically connected to a current collector leading out from the cylindrical wound electrode assembly,
• the insulating ring being interposed between the lid and the terminal plate,
• the lid and the terminal plate being electrically connected to each other within an opening of the insulating ring,
• the lid including an aluminum plate or an aluminum alloy plate,
• the lid having an inclined portion formed to protrude toward the terminal plate, and an outer peripheral portion held between surfaces of the gasket, the outer peripheral portion being thicker than the inclined portion,
• wherein a portion of the lid forms a step disposed radially inward from the inclined portion to protrude toward the opening in the insulating ring, and
• the lid being disposed so as to expose an outer side of at least an entire portion of the lid opposed to the opening of the insulating ring directly to an outside environment.