Nanoporous Nb2O5 coatings enabled long-life and deeply rechargeable zinc anodes for aqueous zinc-ion batteries

For aqueous zinc-ion batteries (AZIBs) with aqueous electrolyte and zinc metal anode, the advantages of high safety, low cost and environmental friendliness make them promising systems for energy storage. However, the problems of dendrite growth derived from non-uniform zinc deposition, hydrogen evolution and corrosion during cycling seriously affect the reliability of the battery and limit its service life. In this work, nanoporous coatings composed of niobium pentoxide (Nb2O5) are designed to modify zinc anode to achieve uniform zinc deposition. The effect of Nb2O5 coatings on the deposition behavior is analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and in situ optical microscopy, which show that Nb2O5 coatings can regulate zinc ion deposition, uniformize the charge distribution, limit the irregular 2-dimensional (2D) diffusion of zinc ions, and inhibit the dendrite growth. Zn|Zn symmetric battery and Zn|Ti battery tests show that Nb2O5- coating Zn anodes (Nb2O5@Zn) can achieve lower polarization voltage, higher Coulombic efficiency and more excellent cycle stability even under an ultra-high current density of 20 mA cm-2. With Nb2O5@Zn anodes, Zn// MnO2 and Zn//V2O5 batteries exhibit higher cycle stability and rate performance, verifying that the Nb2O5 coating strategy is a facile and efficient way to long-life and deeply rechargeable AZIBs.