Zinc-iron (Zn-Fe) redox flow battery single to stack cells: a futuristic solution for high energy storage off-grid applications

The decoupling nature of energy and power of redox flow batteries makes them an efficient energy storage solution for sustainable off-grid applications. Recently, aqueous zinc-iron redox flow batteries have received great interest due to their eco-friendliness, cost-effectiveness, non-toxicity, and abundance. However, the development of zinc-iron redox flow batteries (RFBs) remains challenging due to severe inherent difficulties such as zinc dendrites, iron( iii ) hydrolysis, ion-crossover, hydrogen evolution reactions (HER), and expensive membranes which hinder commercialization. Many scientific initiatives have been commenced in the past few years to address these primary difficulties, paving the way for high-performance zinc-iron (Zn-Fe) RFBs. This review collectively presents the various aspects of the Zn-Fe RFB including the basic electrochemical cell chemistry of the anolyte and catholyte, and the different approaches considered for electrodes, electrolytes, membranes, and other cell components to overcome the above issues. This review summarizes the recent activities and viewpoints for obtaining high-performance Zn-Fe RFBs. Decoupling of energy and power; depth of discharge; flexible in design; high safety; recyclable.