A self-regulated interface enabled by trivalent gadolinium ions toward highly reversible zinc metal anodes

Aqueous zinc-ion batteries (AZIBs) have become an ideal candidate for large-scale energy storage systems owing to their inherent safety and highly competitive capacity. However, severe dendrite growth and side reactions on the surface of zinc metal anodes lead to quick performance deterioration, seriously impeding the commercialization of AZIBs. In this work, a self-regulated zinc metal/electrolyte interface is constructed to solve these problems by incorporating the trivalent Gd³⁺ additive with a lower effective reduction potential into the aqueous ZnSO₄ electrolyte. It is revealed that the inert Gd³⁺ ions preferentially adsorb on the active sites of the zinc anode, and the induced electrostatic shielding layer is beneficial to uniform Zn deposition. Meanwhile, the adsorbed Gd³⁺ ions act as a buffer interface to lower the direct contact of the zinc anode with water molecules, thereby suppressing the interfacial parasitic reaction. These features endow the Zn//Zn battery using 0.2 M Gd³⁺ ions with 2940 h of cycling life at 5 mA cm^-2 and a cumulative plating capacity (CPC) of 6.2 Ah cm^-2 at 40 mA cm^-2. When assembling with a MnO₂ cathode, the full cell using the modified electrolyte exhibits a high capacity of 268.9 mAh/g at 0.2 A/g, as well as improved rate capability and cycle stability. The results suggest the great potential of a rare earth ion additive in reinforcing Zn metal anodes for developing practical AZIBs.