A secondary battery, which can improve reliability by allowing a membrane to be maintained in a short-circuited state until a preset current level is reached, includes an electrode assembly including a first electrode plate and a second electrode plate, a case accommodating the electrode assembly, a cap plate coupled to an opening of the case and electrically connected to the first electrode plate, an electrode terminal including a terminal plate passing through the cap plate and electrically connected to the second electrode plate, and an asymmetrically shaped inversion plate coupled to the cap plate and configured to perform an inversion operation when an internal pressure of the case exceeds a reference pressure.