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 cal-culations 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+-SO42-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 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 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.

Automated summary

Low-cost and high-safety aqueous zinc batteries suffer from irreversibility of the anode. This study uses dimethylacetamide as a water dragger in low-concentration ZnSO4 electrolytes to reshape the solvation structure of Zn2+ ions. The use of dimethylacetamide-hybrid electrolyte improves the coulombic efficiency and cycle lifespan of the batteries, and shows superior rate performance and long-term cyclability in full cells.