SECONDARY BATTERY

The disclosure relates to a secondary battery (10) comprising: a cap assembly (13) comprising a cap plate (131) comprising an electrode lead-out hole (131a) and an electrode terminal (132) disposed on the cap plate and covering the electrode lead-out hole; a current collector (14) comprising a main body (14a) located at a side of the cap plate and an extending portion (14b) extending toward the electrode terminal, wherein the extending portion comprises a top plate (141) connected to the electrode terminal and a side plate (142) connected to the main body, and the side plate and the top plate are configured to form a recess (143); and an insulating protection component (15) comprising a column portion (151) disposed in the recess, wherein surfaces of the side plate and the top plate which form the recess are in contact with and covered by the column portion.