A Highly Water‐Retentive Electrolyte Enabling Stable Aqueous Zinc‐Ion Batteries Across a Wide Temperature Range

Abstract Water‐based batteries employ salt aqueous solutions as electrolytes. However, water molecules are susceptible to evaporation over extended usage or long storage periods. Continuous water loss from electrolytes diminishes ionic conductivity, resulting in accelerated battery degradation. To mitigate these issues, a highly water‐retentive electrolyte (HWRE) is developed by incorporating Di(propylene glycol) methyl ether (DPM) as a co‐solvent. The hydroxyl (─OH) groups in DPM form a hydrogen bonding network with water molecules, effectively stabilizing the electrolyte and reducing its evaporation. This electrolyte formulation has enabled Zn//Zn cells to achieve a cycling life exceeding 4200 h, and Zn//Cu cells maintain an average Coulombic efficiency of 99.8% over 2500 cycles. Moreover, the outstanding water‐retention property of the HWRE enhances battery stability across a wide temperature range of −20 to 40 °C. This HWRE strategy offers insights for the development of safe aqueous batteries.