Enhancement of Electrochemical Performance of Aqueous Zinc‐Ion Batteries Using Hydrated Eutectic Electrolytes

Among various energy storage systems, zinc‐ion batteries (ZIBs) have emerged as promising candidates due to their inherent advantages, such as a low redox potential (−0.763 V vs. SHE), high safety, environmental benignity, high theoretical capacity (820 mAh g − 1 or 5855 mAh cm − 3 ), and low cost. With the rapid development of renewable energy technologies, the demand for ZIBs with high capacity, high voltage, and stable output performance continues to increase, placing increasingly stringent demands on electrode materials and electrolyte systems. This work aims to enhance the performance of ZIBs through electrolyte modification and zinc anode optimization. We engineered the electrolyte through the construction of a hydrated eutectic electrolyte by introducing acetonitrile (AN) as a co‐solvent and formamide (FA) as a functional coordinating molecule. The strong coordination interaction between FA and Zn 2 + effectively displaces coordinated water molecules from the Zn 2 + solvation sheath, thereby suppressing hydrogen evolution reactions during cycling and widening the electrochemical stability window of the electrolyte from 2.52 to 2.61 V. The unique solvation structure and reconstructed hydrogen‐bond network significantly decrease the freezing point of the electrolyte, enabling Zn||Zn symmetric cells to operate stably for 800 h at −10°C. Furthermore, the hydrated eutectic electrolyte promotes reversible Zn 2 + intercalation/deintercalation in MnO 2 . Consequently, the assembled Zn||MnO 2 full cell achieves a discharge specific capacity of 192.3 mAh g − 1 and maintains 92.3% capacity retention after 2200 cycles at a current density of 1 A g − 1 .