Roughness Evolution and Dendritic Growth in Zinc Electrodeposition from Halide Electrolytes. Final Report

摘要

Evolution of rough or dendritic surface texture during electrodeposition often restricts the capacity of rechargeable batteries by limiting the thickness of the plated layer, thereby imposing economic and operating limitations on high energy storage systems such as the zinc-halogen batteries. This technologically important phenomenon has so far been treated mostly empirically. A comprehensive model for roughness evolution in electrodeposition, taking into account the combined effects of transport by diffusion and convection, reaction kinetics and the surface energy is reported here. Critical overpotentials and induction times for roughness initiation, and propagation of roughness elements are determined. Morphological stability analysis explains why certain electrodes remain smooth whereas others evolve dendrites, and defines conditions for smooth deposition. Once roughness evolution is indicated, the complete growth history of the nodules is provided in terms of the current density and the applied potential, the convective flow, chemical composition and the macroscopic and microscopic geometry. The density and distribution of roughness elements evolving over extended electrodes subject to non uniform flow and potential fields are modelled. Severe localized dendritic growth is indicated, well below the limiting current, under certain conditions. Experimental measurements in the electrodeposition of zinc and copper, and reported observations in the literature, are in excellent agreement with the theoretical predictions. (ERA citation 08:031798)