Investigation of Impedance Evolution for Lithium Plating Detection During Multi-Stage Constant Current Fast Charging of Lithium-Ion Batteries

The lengthy charging times of lithium-ion batteries for electric vehicles (EVs) significantly affect their acceptance. Reducing charging time requires high-power fast charging. However, such fast charging can trigger various side reactions, leading to safety and durability issues. Among these, lithium plating is a major concern as it can reduce battery capacity and potentially cause internal short circuits or even thermal runaway. Currently, multi-stage constant current charging (MCCC) protocols are widely adopted. However, the difficulty in effectively detecting lithium plating during the MCCC process significantly limits the charging power. Therefore, it is urgent to explore a method to detect lithium plating during the MCCC process. In this study, the impedance evolution during the MCCC procedure was first investigated. Then a method based on the impedance variation patterns was proposed to detect lithium plating. Besides, the corresponding mechanism was further investigated. Specifically, the experimental results suggest that when lithium plating occurs, it leads to an abnormal decrease in the 1 Hz impedance. This phenomenon is observed across different temperatures and charging rates during the MCCC process. The underlying mechanism was analyzed by the Butler-Volmer equation. Besides, the impedance variation behavior under different charging conditions was explained. By monitoring the trend of abnormal accelerated decrease in 1 Hz impedance, lithium plating can be accurately detected before it significantly deteriorates. Furthermore, this method was integrated into the battery management system (BMS), enabling a closed-loop MCCC protocol. Characterization results show that this method can prevent irreversible lithium plating while shortening charging time. Relaxation voltage and post-mortem analysis validated this conclusion. The impedance-based method provides a feasible solution for non-destructive online lithium plating detection during the MCCC procedure, offering a practical approach for fast charging of EVs.