SECONDARY BATTERY

A secondary battery (100) includes: a case (160) having an internal space; an electrode assembly (110) accommodated in the internal space of the case (160); a current collector plate (120) electrically connected to the electrode assembly (110); and a cap assembly (150). The cap assembly (150) includes: a cap plate (151) sealing the case (160); an electrode terminal (154) coupled to the current collector plate (120) and extending through the cap plate (151); and a gasket (153) between the electrode terminal (154) and the cap plate (151). The gasket (153) has a flange portion (153a), and the flange portion (153a) of the gasket (153) is between an upper surface of the cap plate (151) and the electrode terminal (154).