Enhanced Charge Rate Test Using Impedance-Based Lithium Plating Detection for Reliable Characterization of Structure-Calendered Anodes

Electromobility as a key factor of the energy transition places high demands on its core technology: the lithium-ion cell. In particular, fast charging is one of the critical prerequisites and is associated with major challenges, as improving the fast-charging capability often comes at the cost of reduced energy density. Electrode structuring can enhance the fast-charging capability of lithium-ion cells without compromising energy density. Simple and meaningful characterization methods are essential for rapid development of such processes. However, conventional charge rate tests can lead to misleading results when testing transport-limited electrodes. This study demonstrates that, for transport-limited electrodes, conventional rate tests may yield similar results despite significantly different transport parameters, such as tortuosity. Conventional graphite anodes are compared with electrodes processed via structure calendering - a novel method that combines structuring and calendering within a single roller process step. Using rate tests and half-cell measurements, it is shown how lithium plating contributes to this effect and the underlying electrochemical phenomena are explained. Furthermore, an adapted charge rate test procedure is proposed, which effectively demonstrates the advantage of structured electrodes in the charging direction. The novel method can be implemented using standard cell testers enabling widespread application.