SECONDARY BATTERY

PROBLEM TO BE SOLVED: To provide a secondary battery equipped with a current breaking mechanism suitable for constructing the secondary battery with high capacity and a high output. SOLUTION: The secondary cell is constructed by housing an electrode group 3 formed by winding a positive electrode plate and negative electrode plate through a separator, and jointing a positive electrode current collector plate 14 at one end, and jointing a negative electrode current collector plate 5 at the other end, in an external case 2 formed into a bottomed cylinder shape with a spacer 4 arranged at the positive electrode current collector plate 14 side, and by welding a protrusion part 14a of the positive electrode current collector plate 14 to a bottom part 2b of the external case 2 at a welding point A, and by sealing the opening part of the external case 2 by a sealing member 20. When internal pressure of the battery is increased in accordance with temperature increase of the battery due to overcharge or the like, and swelling generated at the bottom part 2b becomes large, electric connection between the positive electrode current collector plate 14 and the external case 2 is broken by the breakage of the welding point A, and a current circuit is broken. COPYRIGHT: (C)2005,JPO&NCIPI