Patent ID: 8900733

Claim:
A sealed battery comprising: an electrode body that forms a positive electrode and a negative electrode; an electrolyte; and a sealed case that houses the electrode body and the electrolyte, wherein a safety valve that opens when internal pressure of the case rises to equal to or greater than a predetermined value is formed in a portion of the case; wherein the safety valve includes a thin portion formed thinner than the surrounding portion of the safety valve, and a fracture groove portion formed in the thin portion; wherein the thin portion differs in size between a longer direction and a shorter direction, and includes a curved outer edge portion in which at least a portion of an outer edge portion of the thin portion at both ends, or near both ends, in the longer direction is formed so as to the curved; wherein the fracture groove portion includes a center straight groove portion that extends in the longer direction of the thin portion in a center portion of the thin portion, and a pair of side groove portions, each of which is formed on either side in the longer direction of the center straight groove portion and connected to a corresponding longer direction end portion of the center straight groove portion; wherein at least a portion of the side groove portions is formed so as to be curved following the curved outer edge portion; and wherein the side groove portions become thicker in a continuous or stepped manner farther away from the center straight groove portion.