Reference Electrode Reveals Insights on Sodium Metal/Solid Electrolyte Interface Cycling and Voiding Behaviors at High Current Densities and Areal Capacities.

Plating and stripping processes at solid metal electrode/solid electrolyte interfaces are of great significance for high-energy, solid-state batteries. Here, we introduce a Na metal reference electrode to a symmetric Na metal/sodium β″ alumina/Na metal cell and study both cycling and unidirectional protocols with a focus on high current density and areal capacity. For example, in a current ramp test at 5 mAh cm we find a shift from stable to unstable interfacial polarization during stripping at ≳3 mA cm, and at 7.