SECONDARY BATTERY

A secondary battery (100) includes: an electrode assembly (120) including: a first electrode plate (121); a second electrode plate (122); and a separator (123) between the first electrode plate (121) and the second electrode plate (122); a case (110) configured to accommodate the electrode assembly (120); a cap assembly (140) electrically connected to the second electrode plate (122) of the electrode assembly (120); and an insulator (170) coupled to an upper side of the electrode assembly (120), wherein the insulator (170) includes: an insulating upper portion (171) configured to cover the upper side of the electrode assembly (120); an insulating side portion (172) between the case (110) and a side portion (112) of the electrode assembly (120); and an insulating core portion (173) inserted into a hollow portion (125) of the electrode assembly (120) to support the electrode assembly (120).