Potential-Dependent Passivation of Zinc Metal in a Sulfate-Based Aqueous Electrolyte

Owing to its abundance, high theoretical capacity, and low electrode potential, zinc is one of the most important metallic anodes for primary and secondary batteries such as alkaline and zinc-air batteries. In the operation of zinc-based batteries, passivation of the anode surface plays an essential role because the electrode potential of zinc is slightly below that of the hydrogen evolution reaction. Therefore, it is important to scrutinize the nature of the passivation film to achieve anticorrosion inside batteries. Herein, the potential-dependent formation and removal of the passivation film during the deposition and dissolution of zinc metal in aqueous electrolytes are detected via electrochemical quartz crystal microbalance analysis. Film formation was not noticeable in hydroxide-based electrolytes; however, sulfate-based electrolytes induced potential-dependent formation and removal of the passivation film, enabling a superior coulombic efficiency of 99.37% and significantly reducing the rate of corrosion of the zinc-metal anodes. These observations provide insights into the development of advanced electrolytes for safe and stable energy-storage devices based on zinc-metal anodes.