Suppressed Water Reactivity by Zincophilic-Hydrophobic Electrolyte Additive for Superior Aqueous Zn Metal Batteries

As one of the most promising anodes of aqueous batteries, Zn metal faces uncontrollable side reactions and deleterious dendrite growth, which drastically compromise its cycle life and Coulombic efficiency (CE). To tackle these issues, a versatile electrolyte additive is reported that can regulate the solvation structure, adsorb on the Zn surface, and in situ generate a novel zincophilic-microhydrophobic interphase to isolate the anode from the reactive water molecules. Benefiting from its triple effects on the water reactivity modulation, the Zn metal anode exhibits excellent reversibility with an ultra-high average CE value of 99.92% at 5 mA cm-2 in the ZnSO4 electrolyte system, and the Zn||Zn symmetric cell with ethanesulfonamide additive achieves a long lifespan over 6000 h. The merits of ESA additives are further displayed in the Zn//MnO2 full cells and Zn ion hybrid capacitors, exhibiting excellent capacity retention of 81.60% at 5 C over 1000 cycles, and a 92.25% capacity retention over 50 000 cycles at 5 A g-1, respectively. What's more, the full cells exhibit outstanding stability of 100% capacity retention after 120 cycles at 0.1 C. This strategy shows a promising alternative for the further development of aqueous Zn metal batteries with low-cost ZnSO4-based electrolytes. Ethanesulfonamide is introduced into an aqueous ZnSO4 electrolyte to perform a triple effect of water activity suppression, which not only regulates the solvation structure of Zn2+, but also adsorbs on the Zn metal surface to repel the aggregation of water molecules, moreover, it can act as a barrier for water-related side reactions. Thus, an ultra-high plating/stripping efficiency and long cycle stability of 6000 h are achieved.image

Automated summary

By introducing ethanesulfonamide to the aqueous ZnSO4 electrolyte, a triple effect of water activity suppression is achieved, resulting in improved cycle stability and Coulombic efficiency of aqueous Zn metal batteries.