Minimizing solvated water via synergistic effect of salt anion and cosolvent enables stable Zn metal anodes in low-cost acetate electrolyte

• Low-cost, safe and eco-friendly acetate-based electrolyte was prepared. • Investigating synergistic effect of salt anion and cosolvent in solvation structure. • Effectively inhibiting Zn corrosion in medium-concentration acetate electrolytes. • Achieving compact dendrite-free Zn deposition. Aqueous zinc metal batteries (ZMBs) have attracted increasing attention in the past decades owing to their potentially low cost and non-flammability. However, the poor Coulombic efficiency (CE) and short lifespan caused by side reactions (e.g., H 2 evolution) and dendrite growth limit the practical applications of ZMBs. Given that H 2 evolution is primarily originated from solvated water, here, a low-cost acetate-based electrolyte constituted by 1 m ZnAc 2 and 5 m KAc in an 80:20 water:trimethyl phosphate (TMP) (v/v) mixture is proposed to minimize solvated water and boost the electrochemical performance of aqueous ZMBs without compromising intrinsic advantages of the aqueous electrolyte. The relatively high abundance of Ac − enables preferential coordination with Zn 2+ , meanwhile, the addition of TMP not only further replaces water molecules in the inner solvation shell, but also significantly interrupts the H-bond network of water. Improved electrochemical performance are demonstrated in Zn||Zn and Zn||Cu half-cells and Zn||I 2 full cells.