Secondary battery

A secondary battery (100) including an electrode assembly (110) including a first electrode plate (111), a second electrode plate (112), and a separator (113) between the first and second electrode plates (111,112), a case (140) configured to accommodate the electrode assembly (110), and a cap assembly (150) configured to seal the case (140) and including a cap plate (151) having a short-circuit opening, a reversible plate (158) at the short-circuit opening, an insulation member (157) on the cap plate and including an open part at a side, and a short-circuit plate (159) configured to be inserted into and coupled to the open part for covering the short-circuit opening.