A Sorting Method Based On Internal Health Characteristic For Lithium-ion Batteries

As a kind of ideal energy storage device,lithium ion battery has been widely used in electronic products,electric vehicles,aerospace and other fields with its excellent characteristics.In order to meet the requirements of voltage level of the application object,lithium ion battery mostly appears in the form of battery packs.The consistency of cell's performance parameters in the battery pack is one of the key factors that restrict the cycle life of battery pack.This paper proposes a sorting method for lithium ion battery based on its internal health characteristics and compares its sorting effect with traditional sorting criteria.SP+ simplified electrochemical model that can reflect internal working processes was developed.Based on this,the relationship between model parameters and external behavior of battery was analyzed.The model parameters were then obtained by means of stimulus response analysis with no damage to battery.Aging test was performed on lithium ion batteries.Then the law of performance parameters of battery with battery's cycle life was analyzed based on SP+ simplified model and traditional sorting criteria respectively.An in-depth analysis of sensitivity and coefficient of variation of performance parameters of battery was performed.The performance parameters with high correlation with battery's cycle life and high reliability of identification were determined as health characteristics of battery.FCM clustering algorithm was associated with the weight of health characteristics of battery.The FCM algorithm validity index VFS was constructed to judge the best battery classification.As a result,the sorting criteria based on battery's health characteristics allow the cells in the same category to be selected from 120 batteries.Meanwhile,the aging test of same working condition was performed on the sorted battery packs.The results from this research can demonstrate that,compared to conventional sorting criteria,the cells in the battery pack that sorted based on internal health characteristics of battery maintain good consistency and the battery pack has a higher SOH during the aging test.