High performance alkaline zinc-iron flow battery achieved by adoption of advanced organic additive

Alkaline zinc-iron flow batteries (AZIFBs) where zinc oxide and ferrocyanide are considered active materials for anolyte and catholyte are a promising candidate for energy storage systems due to their high cell voltage and cost-effectiveness. However, formation of zinc dendrites in aqueous environment remains a critical challenge that should be addressed. Suppressing formation of zinc dendrites through further inclusion of additives in electrolyte is an effective solution to improve performance and stability of AZIFBs. In this study, 3-[bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO), which is alkanolamine-based organic ligand, is considered the additive, forming stable complex of DIPSO and zinc ion under alkaline conditions. Electrochemical evaluations of electrolytes including DIPSO and zinc ion reveal that DIPSO promotes formation of uniform and densely packed zinc nuclei by accelerating nucleation rate of zinc, and favorable and uniform Zn is deposited. As a result, at a current density of 80mA cm⁻2, electrolyte containing 0.1 M Zn(OH)₄^2- and 1.0 mM DIPSO effectively suppresses formation of zinc dendrite during cycling of AZIFBs, achieving their stable cycle performance and energy efficiency without significant degradation for 530 cycles. Based on that, it is corroborated that DIPSO is an effective additive to suppress formation of zinc dendrite and to establish stable cycle performance of AZIFBs.