Zinc Electrode Shape Change in Alkaline Air Batteries: A validated 2D Model

Abstract

Zinc-air batteries are a promising candidate for stationary energy storage. Zinc metal electrodes are stable in water relying on non-toxic materials and enabling low manufacturing costs. Current experimental research in this field deals with cycle-life limiting effects, such as anode shape change and electrolyte passivation. We contribute to this topic by performing multi-dimensional simulations. Recently, we developed a theory-based model of aqueous alkaline zinc-air batteries that consistently couples the dynamics of its solid, liquid, and gaseous phases. 1D simulations predicted the effects of inhomogeneous zinc oxide nucleation and growth as well as carbonate formation in the electrolyte. We validated the model predictions of discharge voltage and shelf-life. Here, we present the first multi-dimensional simulations of zinc-air batteries and extend our model by simulating zinc shape change. Our 2D simulations of button cells are enabled by local volumeaveraging theory. We present an implementation that deals with the numerical instabilities of a multi-component incompressibility constraint. We validate our model by in-situ tomographies of commercial button cells. To this regard, we compare the voltage profile and the phase distribution during discharge. Finally, we discuss various strategies to enhance cycle-life.