Nitrogen-coordinated iron single atoms porous carbon as multi-functional artificial interface layer to enable self-purified zinc anode for rechargeable zinc-air batteries

Due to the dendrite and side reaction of zinc metal anode, it remains a big challenge for zinc-air battery (ZAB) to achieve high cycle stability and higher energy density. Constructing artificial layer on anode surface is an effective way to improve the above key problems and realize self-purified anode. However, the traditional interfacial layer is difficult to maintain stability in alkaline electrolyte and cannot limit the free diffusion of zinc ions on the electrode surface. Herein, a nitrogen-coordinated iron single atoms porous carbon (Fe-N-MC) modified zinc anode (Fe-N-MC@Zn) is proposed. The layer-by-layer multi-functional Fe-N-MC@Zn displays that the porous Fe-N-MC layer provides a good Zn adsorption site, which further induces rapid and smooth deposition to ensure a self-purified zinc reactivity zone. Besides, the electrode with large specific surface area, abundant multi-type N-C structures and strong Fe-Nx coordination uniformizes the interface electrical filed and creates an electronics-rich local micro-environment to further avoid the continuous accumulation of zinc at the position with high electric field strength. Notably, density functional theory (DFT) reveals that Fe-Nx-C can effectively improve the affinity between the artificial layer and Zn atoms and inhibit the random diffusion of Zn ions. Consequently, the artificial Fe-N-MC layer enables the symmetrical Fe-N-MC@Zn//Fe-N-MC@Zn battery with long-term cycling lifespan of 400 h at 10 mA cm−2 and 1mAh cm−2. The ZABs used Fe-N-MC@Zn as anode shows an extended charge–discharge cycling stability of 500 h with high discharge voltage of 1.24 V and low charging voltage of 1.95 V at 5 m A cm−2. This work provides a new perspective for designing multi-functional interface layer to achieve high performance and high reversibility of purified zinc metal anode.