A secondary battery having a current interrupt device (CID) between a negative current collecting plate and a case of the secondary battery. The secondary battery includes: an electrode assembly including a positive electrode, a separator, and a negative electrode; a case housing the electrode assembly; a cap assembly coupled to the case for sealing the case; a positive current collecting plate connected to the positive electrode and the cap assembly; an insulator in the case adjacent an end plate of the case; and a negative current collecting plate connected to the negative electrode and the end plate of the case, the end plate being curved convexly toward an inner cavity of the case.