“Water‐in‐Deep Eutectic Solvent” Electrolytes for High‐Performance Aqueous Zn‐Ion Batteries

Abstract Aqueous Zn‐ion batteries have been considered as promising alternatives to Li‐ion batteries due to their abundant reserves, low price, and high safety. However, Zn anode shows poor reversibility and cycling stability in most conventional aqueous electrolytes. Here, a new type of aqueous Zn‐ion electrolyte based on ZnCl 2 –acetamide deep eutectic solvent with both environmental and economic friendliness has been prepared. The water molecule introduced in the “water‐in‐deep eutectic solvent” electrolyte could reduce the Zn 2+ desolvation energy barrier by regulating Zn 2+ solvation structure to promote uniform Zn nucleation. Zn anode shows improved electrochemical performance (≈98% Coulombic efficiency over 1000 cycles) in the electrolyte whose molar ratio of ZnCl 2 :acetamide:H 2 O is 1:3:1. The assembled full battery composed of phenazine cathode and Zn anode could stably cycle over 10 000 cycles with a high capacity retention of 85.7%. Overall, this work offers new insights into exploring new green electrolyte systems for Zn‐ion batteries.