Dendrite-free Zn anodes enabled by Sn-Cu bimetal/rGO functional protective layer for aqueous Zn-based batteries

Aqueous Zn-based batteries (AZBs) have drawn widespread attention because of their pronounced merits of low cost, high safety, and high energy density. However, various challenges derived from Zn anodes, such as tremendous volumetric change and growth of dendrites. Herein, a mixed protection layer composed of reduced graphene oxide (rGO) and Sn/Cu dual-metal was modified on Zn foil (rGO-SnCu/Zn) through replacement and subsequent reduction reactions to facilitate the uniform Zn electrodeposition and enhance the cyclic stability of AZBs. The rGO reduced by Zn could realize the high flexibility and large surface area to inhibit the huge electrode dimension change and decrease the local current density. Additionally, dual-metal of Sn and Cu derived from the replacement reaction between Sn4+/Cu2+ and Zn make composite anodes possess excellent zincophilcity. Moreover, the compact and uniform coating structure of rGO-SnCu based layer could effectively protect Zn anode from water or air-attacking. As a result, this novel rGO-SnCu/Zn electrode could endow symmetric Zn-based batteries with lower voltage hysteresis, higher stability, and better rate capability. The corresponding Zn ion hybrid supercapacitors and Zn-air cells both showed excellent performances. This novel method of suppressing Zn dendrites could shed a new way for AZBs with long life spans.