Patent attributes
A nonaqueous electrolyte secondary cell comprises a rolled-up electrode unit 2 composed of a positive electrode 23, a negative electrode 21 and a separator 22 interposed therebetween, and a negative electrode current collector plate 3 and a positive electrode current collector plate 30 joined to the respective ends of the electrode unit 2. The negative electrode collector plate 3 is joined to an edge of the negative electrode 21 projecting at one of the opposite ends of the electrode unit 2. The collector plate 3 has a two-layer structure comprising a copper layer 31 made of copper or an alloy consisting predominantly of copper, and a metal layer made of a metal not forming an intermetallic compound with lithium and having a lower laser beam reflectivity than copper or an alloy consisting predominantly of the metal. The collector plate 3 has its copper layer 31 contacted with the edge of the negative electrode 21 and welded thereto with a laser beam. This improves the weldability of the collector plate 3 to the rolled-up electrode unit 2 to achieve a high current collecting efficiency.
