Patent ID: 7927727

Claim:
A secondary battery, comprising: an electrode assembly having a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; a container providing an interior receiving the electrode assembly; a cap plate for sealing an open end of the container, the cap plate having a hole, a diameter of the hole on a surface of the cap plate being different from a diameter of the hole on another surface of the cap plate, the hole having a stepped surface between portions of the hole having different diameters; a safety valve mounted inside a portion of the hole having a larger diameter of said diameters, the safety valve having a groove formed on a surface of the safety valve facing the interior of the container, the groove formed around a center of the hole, the groove rupturing upon occurrence of an increase of pressure within said interior; and a fastening member arranged on one side of the safety valve disposed in the hole to secure the safety valve, the fastening member being disposed on the stepped surface and the safety valve being disposed on the fastening member.