Competitive Solvation-Induced Interphases Enable Highly Reversible Zn Anodes

Aqueous Zn-metal batteries have been recognized as promising energy storage devices due to their high theoretical energy density and cost-effectiveness. However, side reactions and Zn dendrite growth during cycling limit their practical application. Herein, we investigated methylammonium acetate as an electrolyte additive to enhance the reversibility and stability of the Zn anode. The results revealed that the acetate anions would competitively engage the Zn2+ solvation structure to reduce the water reactivity and promote the anion-enriched structure in the electrolyte, which can efficiently suppress the byproducts and dendrite formation. These occurs thanks to the formation of an anion-derived, robust solid electrolyte interphase with an inorganic/organic hybrid structure. Such an electrolyte enables a long cycle life over 2000 h in the Zn||Zn cell and a high Coulombic efficiency of >99.5% for 700 cycles in the Zn||Ti cell. Therefore, both Zn||Na3V2(PO4)3 batteries and Zn||activated carbon capacitors in this electrolyte exhibit improved cycling performance.