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

The trivalent Gd3+ ions are introduced as electrolyte additives to form an electrostatic shielding layer on the surface of the zinc anode, resulting in a highly stable and reversible zinc metal anode. [Display omitted] • The Gd3+ ions can form an electrostatic shielding layer on the zinc anode to promote the uniform deposition of Zn2+ ions. • The adsorbed Gd3+ ions acted as a buffer interface, reducing the direct contact between the zinc anode and H 2 O and thus inhibiting the interfacial parasitic reaction. • The Zn//Zn and Zn//MnO 2 cells exhibit extended cycle life and enhanced rate capability. 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 ZnSO 4 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 MnO 2 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. [ABSTRACT FROM AUTHOR]