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

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 Zn²⁺ solvation structure. The Ch⁺ cations in choline chloride (ChCl) and glucose integrate into the primary solvation sheath of Zn²⁺, 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.