Engineering interfacial layers to enable Zn metal anodes for aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted increasing attention as promising energy storage devices in large-scale energy storage systems due to their low cost, high capacity, and inherent safety. However, the poor reversibility of zinc anodes has largely restricted their further development because of the dendrite growth, surface passivation, and hydrogen evolution problems associated with Zn metal anodes during the repeated plating/stripping cycles. Surface engineering with functional protection layer appears to be an effective means to mitigate Zn dendrite issues. We first introduce zinc electrochemistry in mild/neutral environments and elaborate Zn anode degradation mechanism. Then, we give state-of-the-art research progress and provide a specific, comprehensive, and in-depth summary of the mechanisms of different coating materials, and share some examples of advanced characterizations for an in-depth understanding on the working mechanisms of the coating layers. Finally, we propose a design principle for the structural design of an ideal interface layer on the Zn metal and share perspectives. This review would give rise to a broad interest focusing on commercial Zn foils in the community of ZIBs, bring potential ideas and inspiration in surface engineering strategies for the rational design of dendrite-free Zn anodes, and boost the development of advanced aqueous ZIBs with low cost and inherent safety.