Study on Consistency of Grouped Secondary Use of Retired Lithium-Ion Batteries Based on Two-Tier Sorting

The sorting into groups is a critical step in the cascade utilization process of retired power lithium-ion batteries. In order to enhance the consistency performance of grouped batteries in cascade utilization, the various static and dynamic features based on battery charge and discharge experimental data are extracted in this paper, A two-tier sorting architecture is established and the combined sorting of static and dynamic features are achieved. In the first-tier sorting, fuzzy logic is employed in combination with static battery characteristics for an initial sorting. The simulated annealing algorithm is used to optimize the initial selection of cluster centers in the K-means algorithm. In the second-tier sorting, an improved K-means algorithm is applied to conduct a secondary sorting based on the dynamic characteristics of the batteries. Following the second-tier sorting, the consistency of open-circuit voltage among battery groups improved by 92%, the consistency of internal resistance improved by 94%, and the consistency of capacity improved by 33%. It can be observed that the approach proposed in this paper effectively enhances the consistency of retired battery grouping.