Lithium ion secondary battery degradation judgment system and degradation judgment method

摘要

An MPU performs a degradation diagnosis based on an open circuit voltage characteristic of a rechargeable lithium ion battery indicating how the battery varies in open circuit voltage as the battery varies in capacity to obtain a capacity ratio (k1) of a positive electrode of the battery, a capacity ratio (k2) of a negative electrode of the battery, and a deviated capacity (”Qs) of the battery (S100). The MPU applies the capacity ratio (k1) of the positive electrode and the capacity ratio (k2) of the negative electrode to a predetermined map for degradation attributed to wear to estimate a deviated capacity (”Qs(W)) resulting from degradation attributed to wear (S110) and separates the deviated capacity (”Qs) into the deviated capacity (”Qs(W)) resulting from degradation attributed to wear and a deviated capacity (”Qs(Li)) resulting from deposition of lithium (S120). The MPU uses at least the deviated capacity (”Qs(Li)) resulting from deposition of lithium to determine whether a rechargeable lithium ion battery subject to determination of degradation is reusable and/or recyclable (S200).