Breaking the Water Activity Barrier: Hydrated Eutectic Electrolytes for Long‐Cycling and Wide‐Temperature Zinc‐Ion Batteries

Abstract The high activity of water molecules in aqueous electrolytes drives detrimental side reactions and Zn dendrite growth, severely limiting the practical application of zinc‐ion batteries (ZIBs). Herein, a biocompatible hydrated eutectic electrolyte is designed to fundamentally confine water activity and reconstruct the Zn ²⁺ solvation structure. The Ch ⁺ cations in choline chloride (ChCl) and glucose integrate into the primary solvation sheath of Zn ²⁺ , displacing coordinated water molecules and reducing the coordination number from 6 to 3.2. This unique solvation structure, combined with water molecules confined within the robust ChCl‐glucose eutectic hydrogen‐bonding network, effectively suppresses the hydrogen evolution reaction (HER), corrosion, and dendrite formation. Consequently, Zn//Zn symmetric cell achieves exceptional cycling stability of 2000 h at 1 mA cm ⁻² . Additionally, the Zn//PANI full cells deliver 82.6% capacity retention after 2000 cycles at 3 A g ⁻¹ and a remarkable power density of 8303.29 W kg ⁻¹ at 10 A g ⁻¹ . Critically, the low glass transition temperature of the eutectic network enables stable operation across an ultra‐wide temperature range (from −20 to 50 °C), overcoming a major limitation of conventional aqueous ZIBs. This work demonstrates a potent strategy of water confinement and solvation engineering via hydrated eutectic electrolytes for practical, high‐performance, and temperature‐resilient ZIBs.