Enhancing electrochemical performance and stabilizing zinc anode in mild acidic electrolyte using combined additive

Abstract

Rechargeable zinc-based batteries having aqueous electrolytes are renowned as promising alternatives for large scale energy storage systems (ESSs). However, in mild acidic electrolytes, zinc anodes pose several issues that have yet to be overcome. For tackling the major difficulties of zinc anodes, electrolyte engineering is the most practical and cost-effective strategy. Notwithstanding the broad variety of mechanisms associated with different electrolyte additives, the function of a single additive is straightforward. Finding combined additives with broader functionalities and greater efficacy is crucial. In this work, the combination of ionic liquid (IL) 1-butyl-1-methylpyrrolidinium dicyanamide ([BMPY][DCN]) and ethylene glycol (EG) as additives in an aqueous electrolyte 3 M ZnSO4 proves to be an effective strategy for simultaneously enhancing both zinc dissolution and deposition. IL significantly enhances zinc (Zn) dissolution and deposition while EG plays an important role in suppressing hydrogen evolution reaction (HER)and corrosion. Thus, 13.50 % improvement in capacity is achieved by the mixed additive EG + IL/ZnSO4 compared with the 3 M ZnSO4 electrolyte. In the Zn//Zn symmetrical system at 2 mA cm−2, the mixed additive greatly augments the cyclability of zinc, reaching over 400 h while maintaining excellent coulombic efficiency (CE). In-situ XAS and FT-EXAFS analyses confirm the high activities of both zinc oxidation/reduction in the mixed additive electrolyte. Results demonstrate that EG + IL/ZnSO4 can be applied to increase the cyclability of aqueous zinc-based batteries while sustaining high performance.