A Water‐Insoluble Yttrium‐Based Complex as Dual‐Ionic Electrolyte Additive for Stable Aqueous Zinc Metal Batteries

Aqueous batteries employing Zinc metal anodes (ZMAs) are considered to be promising next‐generation energy storage systems. However, the severe interfacial side reactions and dendrite growth restrict the practical application of ZMAs in aqueous electrolytes. Herein, a water‐insoluble dual‐ionic electrolyte additive of yttrium 2,4,5‐trifluorophenylacetate (YTFPAA) is developed to stabilize the aqueous ZMAs. Notably, the ethanol‐solvated TFPAA− can capture H+ and thus buffer the decreased electrolyte pH caused by the hydrolysis of Y3+. Furthermore, the ethanol‐solvated TFPAA− can dynamically adsorb onto the surface of ZMAs through a reversible oxidation‐reduction reaction, effectively suppressing the interfacial side reactions by forming a water‐poor interface, and enhancing the reversibility of Zn2+ deposition/stripping by redistributing the Zn2+ flux. These favorable effects of TFPAA− combined with the dynamic electrostatic shielding effect of Y3+ ultimately enable uniform and dense Zn2+ deposition. As a result, the Zn/Zn cells assembled with 0.25YTFPAA electrolyte exhibit an impressive cycle life of 2100 h at 0.5 mA cm−2–0.25 mAh cm−2. More importantly, the assembled V2O5/Zn full cell shows an ultra‐long cycle life of up to 18000 cycles at 5.0 A g−1. This work highlights the rational design of multifunctional ionic additives for stabilizing aqueous ZMAs. A water‐insoluble yttrium 2,4,5‐trifluorophenylacetate (YTFPAA) is developed as the dual‐ionic electrolyte additive. In the YTFPAA‐modified electrolytes, Zn2+ deposition is regulated by the ethanol‐solvated TFPAA− and Y3+, leading to uniform and dense Zn2+ deposition. Furthermore, the dynamic adsorption of the ethanol‐solvated TFPAA− on the surface of the Zn anode can effectively suppress the interfacial side reactions.