A secondary battery, comprising: a cap plate provided with electrode terminals; and at least one cell, each cell comprising a main body and tabs electrically connected to the main body and extending from the main body; wherein the main body of each cell is upright along a thickness direction of the cap plate; characterized in that the secondary battery further comprises: connecting pieces, each connecting piece is electrically conductive and parallel to the cap plate and positioned at an inside of the cap plate in the thickness direction of the cap plate, a longitudinal direction (L') of each connecting piece is parallel to a length direction of the cap plate, a transverse direction (W') of each connecting piece is parallel to the width direction of the cap plate, each connecting piece has: a tab welding portion welded with the corresponding tab of each cell; and an electrode terminal welding portion connected to the tab welding portion along the longitudinal direction (L') of each connecting piece and welded with the corresponding electrode terminal of the cap plate so as to electrically connect the corresponding electrode terminal and the corresponding tab of each cell; and each tab of each cell has: a planar portion parallel to a width direction of the cap plate and welded to the tab welding portion; and an upright portion extending parallel to the main body and connected to the planar portion so as to form a reversed L shape together with the planar portion. a cap plate provided with electrode terminals; and at least one cell, each cell comprising a main body and tabs electrically connected to the main body and extending from the main body; wherein the main body of each cell is upright along a thickness direction of the cap plate; characterized in that the secondary battery further comprises: connecting pieces, each connecting piece is electrically conductive and parallel to the cap plate and positioned at an inside of the cap plate in the thickness direction of the cap plate, a longitudinal direction (L') of each connecting piece is parallel to a length direction of the cap plate, a transverse direction (W') of each connecting piece is parallel to the width direction of the cap plate, each connecting piece has: a tab welding portion welded with the corresponding tab of each cell; and an electrode terminal welding portion connected to the tab welding portion along the longitudinal direction (L') of each connecting piece and welded with the corresponding electrode terminal of the cap plate so as to electrically connect the corresponding electrode terminal and the corresponding tab of each cell; and each tab of each cell has: a planar portion parallel to a width direction of the cap plate and welded to the tab welding portion; and an upright portion extending parallel to the main body and connected to the planar portion so as to form a reversed L shape together with the planar portion. a tab welding portion welded with the corresponding tab of each cell; and an electrode terminal welding portion connected to the tab welding portion along the longitudinal direction (L') of each connecting piece and welded with the corresponding electrode terminal of the cap plate so as to electrically connect the corresponding electrode terminal and the corresponding tab of each cell; and each tab of each cell has: a planar portion parallel to a width direction of the cap plate and welded to the tab welding portion; and an upright portion extending parallel to the main body and connected to the planar portion so as to form a reversed L shape together with the planar portion.