Patent ID: 7968221
Filing Date: 2011-06-28
Classification: H01M,Y02E,Y02P,Y02T

Abstract:
1. A lithium ion secondary battery which comprises: a negative electrode plate in which a negative electrode mixture layer is formed on each of both surfaces of a negative electrode current collector containing copper as a principle component and having a sheet shape; a positive electrode plate in which a positive electrode mixture layer is formed on each of both surfaces of a positive electrode current collector containing aluminum as a principle component and having a sheet shape; and a separator holding an electrolyte, the negative electrode plate, the positive electrode plate and the separator being spirally wound or stacked, wherein: a thickness of the positive electrode current collector is smaller than a thickness of the negative electrode current collector, the lithium ion secondary battery has a weight power density of 1700 W/kg or more, one end portion of the positive electrode current collector is an exposed portion of the positive electrode current collector, and the positive electrode mixture layer is not provided at both surfaces of the exposed portion of the positive electrode current collector, one end portion of the negative electrode current collector is an exposed portion of the negative electrode current collector, and the negative electrode mixture layer is not provided at both surfaces of the exposed portion of the negative electrode current collector, the exposed portion of the positive electrode current collector is located at one end of an electrode plate group for the lithium ion secondary battery, the exposed portion of the negative electrode current collector is located at the other end of the electrode plate group for the lithium ion secondary battery, thickness Da of the positive electrode current collector and thickness Dc of the negative electrode current collector satisfy a relationship of 1.2≦Dc/Da≦2, and the thickness of the positive electrode current collector is 8 μm or more and 25 μm or less.