| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for suppressing the short circuit when charging and discharging a lithium ion secondary battery.SOLUTION: A lithium ion secondary battery comprises: a laminate type electrode group including a rectangular positive electrode 5 and a rectangular negative electrode 6, and a separator 7. The positive electrode 5 includes a current collector foil and a positive electrode mixture layer. The negative electrode 6 includes a current collector foil and a negative electrode mixture layer; a negative electrode active material includes a silicon-based material and a carbonaceous material in the proportion of 20:80 to 80:20 on a mass ratio basis. The silicon-based material is a Si alloy or SiO(0.5≤x≤1.5). The positive electrode 5 and the negative electrode 6 have collector terminals 1 and 2 protruding from a common side of the laminate type electrode group. The negative electrode current collector foil is formed from a stainless steel, a copper alloy including copper and at least one kind element of zirconium, silver and tin, or copper with a purity of 99.99% or higher. As to the lengths of the positive electrode mixture layer and the negative electrode mixture layer in a direction in which the collector terminals 1 and 2 protrude from the common side, the length of the positive electrode mixture layer is equal to or longer than the length of the negative electrode mixture layer.SELECTED DRAWING: Figure 4 |
