High performance of zinc-ferrum redox flow battery with Ac−/HAc buffer solution

A green low-cost redox flow battery using Zn/Zn2+ redox couple in HAc/NaAc medium and Fe2+/Fe3+ redox couple in H2SO4 medium was first proposed and investigated for potential stationary energy storage applications. The presence of HAc/NaAc in the negative electrolyte can keep the pH between 2.0 and 6.0 even when a large amount of H+ ions move into negative electrolyte from positive electrolyte through ion exchange membrane. In the pH range of 2.0–6.0, the chemical reaction of Zn species with H+ species is very insignificant; furthermore, the electroreduction of H+ ion on the negative electrode is significantly suppressed at this pH range. The zinc-ferrum redox flow battery (Zn/Fe RFB) operated within a voltage window of 0.5–2.0 V with a nearly 90% utilization ratio, and its energy efficiency is around 71.1% at room temperature. These results show that Zn/Fe RFB is a promising option as a stationary energy storage equipment.

Graphical abstractHAc/NaAc buffer solution can play an important role to keep pH of Negative electrolyte in the suitable range during the operation of the battery. Figure optionsDownload full-size imageDownload as PowerPoint slide