Roadmap on the protective strategies of zinc anodes in aqueous electrolyte

Rechargeable aqueous zinc (Zn) batteries have captured extensive attentions as auspicious next generation energy storage devices due to the merits of low cost, high capacity, inherent safety, and abundant resources. However, the humble poor durability and low coulombic efficiency of Zn anodes seriously hinder their wide applications. Zn batteries can be classified into two classifications: alkaline and neutral Zn batteries, according to the nature of electrolyte. Due to the different electrochemical behaviors of Zn anodes in the alkaline and neutral electrolytes, the fundamental comprehensions of Zn anodes in both electrolytes remain dubious. In this review, the fundamental reactions of Zn anodes in alkaline and neutral electrolytes were elucidated in detail. Specifically, the primary reasons (including surface passivation, dendritic growth, hydrogen evolution, and shape change in the Zn stripping/plating procedure) which lead to the pitiable durability and low coulombic efficiency of Zn anodes in both electrolytes were profoundly illuminated, respectively. Moreover, the most recent progresses about the Zn anodes protective strategies to settle the above critical problems were systematically recapitulated and clarified, including the surface modification, structural and constitution design, electrolyte modification and other protective strategies. Finally, the challenges and opportunities in high-performance Zn anodes are further expected. This review will shed light on the exploit of advanced Zn anodes for high-performance Zn batteries in both alkaline and neutral electrolytes.