Patent ID: 7425386
Filing Date: 2008-09-16
Classification: H01M,Y02E,Y02P

Abstract:
1. An electrode group for a battery comprising a positive electrode and a negative electrode wound into a spiral with a separator interposed therebetween, wherein said positive electrode includes a positive electrode current collector and positive electrode material mixture layers formed on both sides of said positive electrode current collector, said negative electrode includes a negative electrode current collector and negative electrode material mixture layers formed on both sides of said negative electrode current collector, one of said positive electrode and said negative electrode serving as the outermost turn of said electrode group has: a double side exposed current collector part ranging from the lengthwise end thereof to a predetermined position inside along the winding direction, on both sides of which the positive or negative electrode material mixture layer is not formed; and a single side exposed current collector part continued from said double side exposed current collector part to a predetermined position inside along the winding direction, only on an inner circumference side of which the positive or negative electrode material mixture layer is formed, said double side exposed current collector part and said single side exposed current collector part opposing at least partially to each other without the interposition of the other of said positive electrode and said negative electrode which does not serve as said outermost turn, a lead is connected to said double side exposed current collector part, a lengthwise end of said separator lies inside along the winding direction from said lead, and a plurality of step portions, at least one of said step portions having difference in level formed in said electrode group by lengthwise ends of said current collector part serving as the outermost turn and said separator, respectively, are covered with an insulating member from an inner side of said electrode group, wherein said insulating member is interposed between said separator and said single side exposed current collector part.