Electrolyte engineering strategies for regulation of the Zn metal anode in aqueous Zn-ion batteries

Rechargeable aqueous zinc-ion batteries (AZBs), with their high theoretical capacity, low cost, safety, and environmental friendliness, have risen as a promising candidate for next-generation energy storage. Despite the fruitful progress in cathode material research, the electrochemical performance of the AZB remains hindered by the physical and chemical instability of the Zn anode. The Zn anode suffers from dendrite growth and chemical reactions with the electrolyte, leading to efficiency decay and capacity loss. Recently, significant effort has been dedicated to regulating the Zn anode. Electrolyte manipulation, including tailoring the salt, additives, or concentration, is a useful strategy as the electrolyte strongly influences the anode's failure processes. It is thus worthwhile to gain an in-depth understanding of these electrolyte-dependent regulation mechanisms. With this in mind, this review first outlines the two main issues behind Zn anode failure, dendrite growth, and side reactions. Subsequently, an understanding of the electrolyte tailoring strategy, namely, the influence of the salt, additive, and concentration on the Zn anode, is provided. We conclude by summarizing the future prospects of the Zn metal anode and potential electrolyte-based solutions.