A Comprehensive Review of Health Indicators of Li-ion Battery for Online State of Health Estimation

Lithium-ion batteries have been widely used in various applications, especially in electric vehicles and battery energy storage systems (BESS). Reliable and accurate estimation of battery online state of health (SOH) becomes increasingly important. To realize this task, a variety of approaches have been proposed and several review papers have been addressed to summarize and classify these approaches. To the best of our knowledge, all current works concentrate on classifying estimation methods while no work has been done to review the health indicators (HIs) that are used for estimation. Classifying the HIs by how they are extracted, however, is of great importance because each HI is only effective in specific application situations. This paper, therefore, is to comprehensively review the existing HIs and make a classification based on how they are extracted and where they can be effectively used.