Patent ID: 8293400

Claim:
A battery comprising: a power generation element; a case member that accommodates the power generation element, the case member having a bottom, a side and an elongated opening edge; and an opening closure member that closes the case member, the opening closure member having a case contact part directly contacting the opening edge around an entire periphery thereof, and a case inside part projecting toward an inside of the case member from a portion of a surface of the opening closure member on the case member side internally of the case contact part, wherein the case inside part substantially surrounds an entire periphery of the opening closure member, wherein the case inside part has two narrower portions positioned at both ends of the case inside part in a longitudinal direction of the elongated opening edge of the case member and spaced from an inner surface of the side of the case member, and a wider portion positioned between the two narrower portions and directly contacting an inner surface of the side of the case member.