Exploring the unknown relationship between additives and zinc anodes: from key challenges to enhancement mechanisms

Aqueous zinc-ion batteries (AZIBs) with high ionic conductivity, high theoretical capacity and environmental friendliness are receiving widespread attention as promising large-scale energy storage facilities. However, in aqueous electrolytes, irreversible dendrite growth and side reactions on the anode significantly reduce the performance and cycle life of AZIBs. Therefore, researchers have attempted to enhance anode performance and improve battery stability and reversibility through simple and efficient additive modification methods. However, reviews on the mechanisms of additive modification of zinc anodes are still scarce. Therefore, this review begins with an overview the anode issues in AZIBs and the principles behind them. Subsequently, the mechanisms and latest advancements of additive-protected anodes are comprehensively discussed. These include modifying the solvation structure, reconfiguring the hydrogen-bonding network of the electrolyte, forming an adsorbed layer on the anode surface, promoting the formation of the solid electrolyte interphase (SEI), and generating steric hindrance effects. Notably, this paper also innovatively summarizes the steric hindrance effect of additives, filling a gap in this area. Finally, the remaining problems and future development directions of additive modification methods are discussed, which are important references for the selection, design, and in-depth study of additives as well as the commercial application of AZIBs. • The key strategies of additives to improve the electrochemical properties of zinc metal anodes are systematically summarized. • Typical characteristics of additives under different modification mechanisms are pointed out. • Challenges and future development directions for additives are presented.