| 摘要 |
PROBLEM TO BE SOLVED: To provide: a lithium ion secondary battery having a high capacity and a long life and superior in safety; and a using method thereof.SOLUTION: A lithium ion secondary battery comprises: an electrode body including a positive electrode, a negative electrode and a separator; and a nonaqueous electrolyte. The negative electrode has a negative electrode mixture layer including graphite as a negative electrode active material, of which the capacity per unit area is 2.5 mAh/cmor more, and the usable capacity is a particular value. As to a cell prepared by enclosing, in a battery case, an electrode body A arranged by cutting the above electrode body to form a section and a nonaqueous electrolyte identical to the above nonaqueous electrolyte in composition, provided that the battery case allows the section of the electrode body to be observed visually, in the case of charging the cell with a constant current at a charge rate of 1 C, a part of the graphite of the negative electrode mixture layer located in a particular region of the negative electrode mixture layer, and identified in in-situ observation of the end face by a microscope with a white light source immediately after the voltage of the cell which is being charged reaches a rated upper limit voltage of the lithium ion secondary battery is specified in hue condition. |
