Identification of Lithium-ion Battery Degradation under Fast Charging Protocols

Lithium-ion (Li-ion) batteries have been employed as the most effective energy storage method. However, the efficiency of Li-ion batteries is limited by the charge current. Shortening the charging time as well as extending the lifetime of Li-ion batteries become urgent for electric vehicles. A multi-step fast-charging protocol was designed to extend the lifetime by 40% and reduce charging time by 25% compared to the commonly used charge protocol. In this study, internal resistances and electrochemical impedance spectroscopy were examined across various current cycles. Subsequent post-mortem analyses unveiled a correlation between heightened mechanical stress on graphite anodes and increased current, leading to the graphite exfoliation and a rise in internal resistance. Based on internal resistance analysis and post-mortem analysis validation, full cell fast charge methods were designed and identified aging mechanisms. Multistep fast charge will enhance the charging speed without sacrificing the state-of-health (SOH).