Ionic liquid-regulated stable interphase engineering toward long-life dendrite-free aqueous Zn-ion batteries

Aqueous Zn-ion batteries (AZIBs) represent promising candidates for large-scale energy storage, owing to their exceptional inherent safety and low cost. However, parasitic reactions, including the hydrogen evolution reaction (HER) and uncontrolled Zn dendrite growth, significantly compromise the cycle life of Zn anodes. In this work, we employ 1-ethyl-3-methylimidazolium diethyl phosphate ([EMIM][DEP]) as a multifunctional ionic liquid additive in the aqueous electrolyte. The unique characteristic of [EMIM][DEP] lies in the coordination-film-forming synergy of its diethyl phosphate anion ([DEP]^-), which, together with the interfacial regulation afforded by the [EMIM]⁺ cation, contributes to a ternary synergistic optimization mechanism. This mechanism is distinct from the conventional "single shielding" or "sacrificial decomposition" approaches of fluorinated or sulfonate-based ionic liquids, as it enables a trinity regulation of solvation structure reconstruction, interphase engineering, and zincophilic ion transport. This synergistic strategy effectively overcomes the limitations of traditional additives, including limited interfacial modulation and poor film stability, thereby significantly extending the cycling lifespan of AZIBs. Consequently, the Zn||Zn symmetric cell exhibits exceptional cycling stability for over 5000 h (1 mA cm^-2, 1 mAh cm^-2), while the Zn||PANI full cell retains 98.54% of its capacity after 2000 cycles. Overall, this study elucidates the three-in-one synergistic mechanism mediated by [EMIM][DEP], providing strategic insights for the design of practical high-performance Zn-ion batteries with long cycling life.