Fast charging of lithium-ion batteries requires high current rates, which can lead to unwanted side reactions like metallic lithium deposition (LD). LD accelerates cell aging and causes irreversible capacity loss and should therefore be avoided. To address this challenge, multi-stage constant current (MSCC) charging protocol offers an advanced fast-charging approach that considers battery aging, helping to mitigate the risks associated with LD.
In our study, operando impedance spectroscopy is used to parameterize a voltage threshold based MSCC charging method for a commercial 18650 high-energy LIB with graphite/SiOx blend anode. Starting from a single-stage constant current charging process, considering various initial currents, a multi-stage process is developed to define voltage thresholds at which the charging current must be reduced to avoid metallic lithium deposition. For this purpose, observed impedance anomalies in the time-varying impedance data at a frequency of 78 Hz are used as an indication of the occurrence of parasitic reactions. The voltage at which the impedance anomaly occurred is used as the switch voltage for the MSCC charging profile. In this way, three-staged charging profiles are generated, which avoids or reduces the occurrence of LD. The correct implementation of the voltage-based switches is validated via differential voltage analysis. Charging times are analysed for the different profiles and compared to standard constant current charging profiles.