A secondary battery, comprising: a casing, which includes a receiving hole having an opening; a top cover assembly, which includes a top cover plate connected to the casing to close the opening; an electrode assembly, which is disposed within the receiving hole, the electrode assembly includes two end faces which are opposed to each other in a first direction perpendicular to an axial direction of the receiving hole and tabs extending from the end faces, the electrode assembly further includes two or more electrode units which are laminated in the axial direction, and in a second direction perpendicular to the axial direction and the first direction, a dimension of the tab is smaller than a dimension of the end face; and a current collecting member, which is electrically connected to the tab, wherein the electrode unit has two wide faces and two narrow faces connecting the two wide faces, an area of each of the two wide faces is larger than an area of each of the two narrow faces, the two wide faces are disposed to be opposite to each other in the axial direction, and the two wide faces and the two narrow faces are alternately disposed; and wherein the current collecting member includes a connecting portion disposed between the end face and the casing, the connecting portion has a first sheet extending along the axial direction and a current collecting piece through which the tab is electrically connected to the first sheet, the current collecting piece and the tab are folded with respect to the first direction such that the tab is connected to a surface of the current collecting piece facing away from the end face. a casing, which includes a receiving hole having an opening; a top cover assembly, which includes a top cover plate connected to the casing to close the opening; an electrode assembly, which is disposed within the receiving hole, the electrode assembly includes two end faces which are opposed to each other in a first direction perpendicular to an axial direction of the receiving hole and tabs extending from the end faces, the electrode assembly further includes two or more electrode units which are laminated in the axial direction, and in a second direction perpendicular to the axial direction and the first direction, a dimension of the tab is smaller than a dimension of the end face; and a current collecting member, which is electrically connected to the tab, wherein the electrode unit has two wide faces and two narrow faces connecting the two wide faces, an area of each of the two wide faces is larger than an area of each of the two narrow faces, the two wide faces are disposed to be opposite to each other in the axial direction, and the two wide faces and the two narrow faces are alternately disposed; and wherein the current collecting member includes a connecting portion disposed between the end face and the casing, the connecting portion has a first sheet extending along the axial direction and a current collecting piece through which the tab is electrically connected to the first sheet, the current collecting piece and the tab are folded with respect to the first direction such that the tab is connected to a surface of the current collecting piece facing away from the end face.