Fast Reaction Kinetics and Commendable Low-Temperature Adaptability of Zinc Batteries Enabled by Aprotic Water-Acetamide Symbiotic Solvation Sheath

Although rechargeable aqueous zinc batteries are cost effectiveness, intrinsicly safe, and high activity, they are also known for bringing rampant hydrogen evolution reaction and corrosion. While eutectic electrolytes can effectively eliminate these issues, its high viscosity severely reduces the mobility of Zn2+ ions and exhibits poor temperature adaptability. Here, we infuse acetamide molecules with Lewis base and hydrogen bond donors into a solvated shell of Zn[(H2O)6]2+ to create Zn(H2O)3(ace)(BF4)2. The viscosity of 1ace-1H2O is 0.032 Pa s, significantly lower than that of 1ace-0H2O (995.6 Pa s), which improves ionic conductivity (9.56 mS cm-1) and shows lower freezing point of -45 degrees C, as opposed to 1ace-0H2O of 4.04 mS cm-1 and 12 degrees C, respectively. The acidity of 1ace-1H2O is approximate to 2.8, higher than 0ace-1H2O at approximate to 0.76, making side reactions less likely. Furthermore, benefiting from the ZnCO3/ZnF2-rich organic/inorganic solid electrolyte interface, the Zn || Zn cells cycle more than 1300 hours at 1 mA cm-2, and the Zn || Cu operated over 1800 cycles with an average Coulomb efficiency of approximate to 99.8 %. The Zn || PANI cell cycled over 8500 cycles, with a specific capacity of 99.8 mAh g-1 at 5 A g-1 at room temperature, and operated at -40 degrees C with a capacity of 66.8 mAh g-1. A mild zinc fluoborate-based aqueous electrolyte was developed by modifying the solvation sheath of Zn2+, leading to a more stable electrode/electrolyte interface and accelerated Zn2+ transfer kinetics. Joint participation in solvation process of water-acetamide-anions (Zn(H2O)3(ace)(BF4)2) significantly decreases the freezing point to -45 degrees C, extends the electrochemical stability window to 2.1 V and facilitates ZnCO3/ZnF2-rich inorganic/organic solid electrolyte interface.image