A secondary battery, comprising: a housing comprising a receiving hole with an opening; a top cover assembly hermetically connected with the housing to close the opening; an electrode assembly disposed in the receiving hole, and comprising two end faces opposite to each other in a first direction perpendicular to an axial direction of the receiving hole and a pole tab extending from one of the end faces, wherein the electrode assembly comprises two or more electrode units stacked along the axial direction, and a size of the pole tab is smaller than a size of each of the end faces along a second direction perpendicular to the axial direction and the first direction; a current collector comprising a main body at least partially located between one of the end faces and the housing, wherein the main body extends along the axial direction and is electrically connected with the pole tab, and the main body and the pole tab are at least partially overlapped along the second direction, the current collector further comprises a current collecting sheet used to be connected and fixed with the pole tab, and both the current collecting sheet and the pole tab are located on the same side of the main body in the second direction, a number of the electrode assemblies is set as two, the two sets of the electrode assemblies are stacked along the axial direction, a number of the current collecting sheets is set as two, the two current collecting sheets are disposed to be spaced apart along the axial direction, the pole tab of one set of the electrode assembly and the pole tab of the other set of the electrode assembly are respectively connected with the two current collecting sheets, and the pole tab of the one set of the electrode assembly and the pole tab of the other set of the electrode assembly are at least partially overlapped in the axial direction, each set of the electrode assembly comprises two electrode units that each comprises a sub-end face and a sub-pole tab extending from the sub-end face, two sub-end faces on the same side form one of the end faces, two sub-pole tabs with the same polarity converge to form the pole tab, and the sub-pole tab of one electrode unit extends out of an area of the sub-end face close to the other electrode unit in the axial direction, and each of the electrode units comprises two wide surfaces and two narrow surfaces connecting the two wide surfaces, the two wide surfaces are opposed to each other in the axial direction, the two narrow surfaces are arranged opposite to each other in the second direction, one of the wide surfaces and one of the narrow surfaces are alternately disposed; the pole tab extends out of an area of one of the end faces close to two adjacent wide surfaces of the two electrode units. a housing comprising a receiving hole with an opening; a top cover assembly hermetically connected with the housing to close the opening; an electrode assembly disposed in the receiving hole, and comprising two end faces opposite to each other in a first direction perpendicular to an axial direction of the receiving hole and a pole tab extending from one of the end faces, wherein the electrode assembly comprises two or more electrode units stacked along the axial direction, and a size of the pole tab is smaller than a size of each of the end faces along a second direction perpendicular to the axial direction and the first direction; a current collector comprising a main body at least partially located between one of the end faces and the housing, wherein the main body extends along the axial direction and is electrically connected with the pole tab, and the main body and the pole tab are at least partially overlapped along the second direction, the current collector further comprises a current collecting sheet used to be connected and fixed with the pole tab, and both the current collecting sheet and the pole tab are located on the same side of the main body in the second direction, a number of the electrode assemblies is set as two, the two sets of the electrode assemblies are stacked along the axial direction, a number of the current collecting sheets is set as two, the two current collecting sheets are disposed to be spaced apart along the axial direction, the pole tab of one set of the electrode assembly and the pole tab of the other set of the electrode assembly are respectively connected with the two current collecting sheets, and the pole tab of the one set of the electrode assembly and the pole tab of the other set of the electrode assembly are at least partially overlapped in the axial direction, each set of the electrode assembly comprises two electrode units that each comprises a sub-end face and a sub-pole tab extending from the sub-end face, two sub-end faces on the same side form one of the end faces, two sub-pole tabs with the same polarity converge to form the pole tab, and the sub-pole tab of one electrode unit extends out of an area of the sub-end face close to the other electrode unit in the axial direction, and each of the electrode units comprises two wide surfaces and two narrow surfaces connecting the two wide surfaces, the two wide surfaces are opposed to each other in the axial direction, the two narrow surfaces are arranged opposite to each other in the second direction, one of the wide surfaces and one of the narrow surfaces are alternately disposed; the pole tab extends out of an area of one of the end faces close to two adjacent wide surfaces of the two electrode units.