Method—Impedance Modeling of Lithium Plating During Fast Charging of Lithium-Ion Cells to Derive Monitoring Strategies

Lithium-ion batteries play a key role in electrifying the transport sector. However, short charging times are crucial for consumers to accept battery electric vehicles (BEV). Fast charging makes the battery vulnerable to lithium plating, which leads to rapid cell aging and can cause a thermal runaway. Hence, a strict criterion in the optimization and adaption of fast charging processes is avoiding lithium plating. Simple plating detection methods are needed to optimize and adjust charging strategies precisely. In this study, a stepwise simplification of a lithium plating detection method from a three-electrode setup to a full cell setup is deduced. An equivalent circuit model is used to explain a sudden drop in cell impedance during fast charging, which is a characteristic feature of the lithium plating onset. This feature also appears in the full cell impedance and can be observed by measuring the impedance at one single frequency. Suitable frequencies lie in a low frequency range, where the measurements can be performed with simple devices that may be integrated into a BEV’s battery management system (BMS). Measuring the lithium plating behavior during operation over its lifespan allows continuous adjusting of the charging strategy, which enables faster charging and improves safety.