Hydrated solvation suppression of zinc ions for highly reversible zinc anodes

Low-cost and high-safety aqueous zinc batteries are promising for large-scale energy storage applications. However, the actual performance of aqueous zinc batteries is hampered by the irreversibility of the zinc metal anode originating from the dendrite growth and side reactions, which are associated closely with the hydrated solvation sheath of Zn²⁺ ions in aqueous electrolytes. Here, dimethylacetamide is employed as a water dragger agent in low-concentration ZnSO₄ electrolytes to reshape the solvation structure of Zn²⁺ ions. Theoretical calculations and experimental investigations reveal that a low fractional addition of dimethylacetamide in aqueous ZnSO₄ electrolytes performs strong interactions with water molecules and Zn²⁺ ions, which inhibits hydrated Zn²⁺–H₂O solvation, facilitates Zn²⁺-SO₄^2- association and captures free water molecules via H-bonds formation. The coulombic efficiency of Zn plating/stripping is improved from 94.3% to 98.1% and can be stabilized at 99.5% over 200 cycles with the hybrid electrolyte. The cycle lifespan of the Zn symmetric cell is prolonged over 1000 h at 1 mA cm⁻² and over 450 h at 5 mA cm⁻² with the dimethylacetamide -hybrid electrolyte, which are over fourfold higher than that of the pristine ZnSO₄ electrolyte. Moreover, when the designed electrolyte is incorporated in full cells, the Zn-MnO₂ cell exhibits an improved rate performance and an excellent long-term cyclability with a capacity-retention rate of 81% over 2,000 cycles at 1 A g⁻¹. This work provides a feasible strategy for the development of highly stable aqueous zinc batteries.