| 摘要 |
PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery system in which precipitation of lithium metal on a negative electrode can be determined precisely.SOLUTION: The lithium ion secondary battery system has a lithium ion secondary battery 1 including a positive electrode, a negative electrode, a nonaqueous electrolyte, and a reference electrode, and a control unit 2 for controlling the lithium ion secondary battery. The control unit 2 charges the lithium ion secondary battery with a current value of 10 C or more for a predetermined time, and discharges the lithium ion secondary battery with the same current value as that during charge for a predetermined time after charge. When a first potential difference, i.e., the difference of the negative electrode potential before and after charge is larger than a second potential difference, i.e., the difference of the negative electrode potential after and before discharge, the control unit 2 determines that lithium metal has precipitated on the negative electrode. |
