Multifunctional Hydrated Deep Eutectic Electrolyte Enables Aqueous Zinc-Ion Batteries Operating across a Wide Temperature Range

The practical application of aqueous zinc-ion batteries (AZIBs) is severely limited by their poor adaptability to extreme temperatures, stemming from the high freezing point, low boiling point, and high activity of water in conventional electrolytes. To address this, we propose a hydrated deep eutectic electrolyte (HEE) design strategy. By formulating zinc trifluoromethanesulfonate (Zn(OTf)2), 2-pyrrolidone (PD), and acetamide (ACE) at an optimal molar ratio with water, a high-performance electrolyte (ZAP50) is developed. This system operates through a triple synergistic mechanism: (1) reconstructing the Zn2+ solvation sheath to accelerate desolvation kinetics; (2) forming a robust 3D hydrogen-bonded network to immobilize free water, suppressing hydrogen evolution and corrosion and broadening the liquid range; and (3) inducing the in situ formation of a bilayer solid electrolyte interphase (SEI) to promote uniform Zn deposition. Consequently, batteries employing the ZAP50 electrolyte demonstrate stable operation across a wide temperature range from −20 to 60 °C. The Zn//Zn symmetric cell with ZAP50 achieves exceptional cycling stability over 850 h at 25 °C, over 1200 h at −20 °C, and over 2000 h at 60 °C. The Zn//Cu half-cell exhibits an average Coulombic efficiency of 99.4% over 1200 cycles. When paired with a polyaniline cathode, the full cell retains 92.6% capacity after 1000 cycles at 25 °C and operates stably over 1000 cycles at both −20 and 60 °C, far outperforming cells with a conventional aqueous electrolyte. This work provides a viable electrolyte engineering strategy for high-performance, wide-temperature-range AZIBs.