The present invention relates to a secondary battery and a battery module. The secondary battery includes: a casing including a receiving cavity having an opening; a top cover assembly, and an electrode assembly disposed in the receiving cavity, wherein the electrode assembly includes two end faces disposed opposite to each other in a first direction perpendicular to a depth direction of the receiving cavity, a lug extending from each end face; the lug is a layered structure and has a redundant section near the end face and a connecting section connected to the redundant section; the current collecting member includes a current collecting portion fixedly connected to the connecting section. The lug of the secondary battery of the embodiment of the present invention has the redundant section, which can effectively buffer the movement and reduce the possibility that the lug is torn or broken due to an excessive tensile stress.