Elucidating Zn, Mg, and Ca Electrodeposition Mechanisms in Nonaqueous Electrolytes for Next-Generation Metal Batteries

Abstract

Due to their significantly higher volumetric capacity, natural abundance, and decreased cost compared to Li metal, Zn, Mg, and Ca rechargeable metal batteries in nonaqueous electrolyte solutions have been the subject of extensive research and development. In this study, we employ the electrochemistry and computational simulation to examine the reversible electrodeposition processes of multivalent metals in nonaqueous electrolytes. Cyclic voltammetry (CV) obtained from Zn electroplating/stripping at an ultramicroelectrode (UME) shows that current density and scan rate are independent as predicted from a simple electron transfer process. However, CVs obtained from Mg and Ca deposition/stripping processes at an UME displays an inverse dependence between current density and scan rate. COMSOL simulations suggest that Zn deposition is governed by a one−step two−electron (E) transfer process while Mg and Ca plating requires a chemical step prior to electron transfer step, suggesting a chemical−electrochemical (CE) mechanism.