Influence of Interfacial Voids and Grain Boundary Conductivity on Depletion Kinetics of Sodium Metal Anodes in All-Solid-State Batteries

Abstract

An electrochemical micro-scale phase-field model is developed to simulate the stripping and plating kinetics of a Na-metal anode in all-solid-state Na-ion batteries. In this model, in addition to the metallic anode and ceramic separator regions, a highly conductive but Na-poor region representing the free space is assumed to simulate the shrinking of the Na-anode during electro-stripping and its growth during plating. For a perfect anode/separator interface, we find that the growth and depletion kinetics are linear. However, the presence of multiple interfacial voids at the anode/separator interface causes deviation from this linear behaviour. Finally, we show that depletion kinetics is also proportional to the ratio of the grain boundary conductivity to that of the grain conductivity (σgb/σg) in the separator phase, either with or without interfacial voids.