Lithium Plating Reversibility in Lithium-Ion Batteries Under Subzero Temperature Charging Pulses

Despite lithium plating being comprehensively studied, as one of the most severe degradation mechanisms, significant gaps remain in understanding the interplay between reversible and irreversible plating. A non-invasive detection method is the two-plateau feature in the relaxation voltage. We explored the effects on this feature of individual and successive charge pulses at different C-rates, states of charge, rest and pulse duration, recent history, and ambient temperature down to −40 °C. Thermal heterogeneity impact was negligible, proven using an instrumented cell with an internal thermocouple. While our results agree with the theory that the plateau duration is linearly proportional with the amount of chemically intercalating lithium, they demonstrate a strong influence by temperature, current, phase transitions and recent history. Plating appears to occur easier on already plated lithium, manifesting as a lower instantaneous cell resistance when charging further, before chemical intercalation has finished. Degradation Mode Analysis was used to quantify and distinguish between reversible and irreversible lithium plating for the first time. Irreversible loss appeared related to the time plated lithium is in contact with electrolyte and temperature. The results highlight the importance of highly controlled conditions when studying plating and will aid engineers to design new control and thermal management strategies.