Current Status of Research on Factors Causing Lithium-ion Battery Packs Performance Degradation and their State of Health Estimation

A lithium-ion battery pack is mainly made up of battery cells, battery management system, connector, thermal cooling system and other components. Among them, battery cell is the most fundamental unit of a battery pack, while a battery management system (BMS) is responsible for monitoring and managing the charging-discharging process of a battery pack. Estimating State of health (SOH) is a key component of a BMS. As it is affected by many factors, it is a great challenge to estimate the SOH of a whole battery pack. Reasons causing lithium-ion battery packs performance degradation and approaches to estimating their SOH are summarized, based on reading and collating related literature at home and abroad in recent years. Finally, an outlook on the future research direction is put forward after an overall comparison of the characteristics and shortcomings of different estimation approaches.