A secondary battery includes an electrode assembly including a first electrode, a second electrode, a separator between the first and second electrodes, a first electrode tab connected to the first electrode, and a second electrode tab connected to the second electrode, a case that accommodates the electrode assembly and includes a top opening exposing an upper surface of the electrode assembly and a bottom opening exposing a lower surface of the electrode assembly, a cap plate combined with the case to cover a portion of the top opening, the cap plate having a conducting hole through which a remaining portion of the top opening of the case is exposed, an upper terminal plate above the cap plate and electrically connected to the first electrode tab through the conducting hole, and a lower terminal plate below the case and electrically connected to the second electrode tab through the bottom opening.

The present application provides a new type of cap for a cylindrical lithium battery, which includes a steel sheet, an explosion-proof sheet, a connection piece, a spacer ring and a seal ring. The steel sheet is defined with a through hole. The explosion-proof disc is arranged on one side of the steel sheet, and the explosion-proof disc is provided with a wrap edge, and the wrap edge is extended from an edge of the steel sheet to another side of the steel sheet and then to an edge of the through hole. The middle portion of the connection piece is in contact with the middle portion of the explosion-proof disc. The spacer ring is arranged between the explosion-proof disc and the connection piece. The seal ring is arranged around the explosion-proof disc, the connection piece and the spacer ring.

The present application provides a new type of cap for a cylindrical lithium battery, which includes a steel sheet, an explosion-proof sheet, a connection piece, a spacer ring and a seal ring. The steel sheet is defined with a through hole. The explosion-proof disc is arranged on one side of the steel sheet, and the explosion-proof disc is provided with a wrap edge, and the wrap edge is extended from an edge of the steel sheet to another side of the steel sheet and then to an edge of the through hole. The middle portion of the connection piece is in contact with the middle portion of the explosion-proof disc. The spacer ring is arranged between the explosion-proof disc and the connection piece. The seal ring is arranged around the explosion-proof disc, the connection piece and the spacer ring.