Will Iron Forge the Future of Metal‐Air Batteries in Grid Scale Energy Storage?

Abstract The community is exploring sustainable alternatives for grid‐scale energy storage. Besides lithium‐ion batteries (LIBs), such technologies with a focus on sustainability aspects offer only a limited solution for grid‐scale energy storage. Rechargeable metal‐air batteries (MABs) based on affordable abundant multivalent metal anodes in aqueous medium provide promising theoretical metrics, such as volumetric capacity, but do not completely fulfill their potential when scaled from lab to commercial products. Both the metal anode and the air cathode need to be addressed: corrosion, hydrogen evolution reaction (HER) during charging, and passivation all diminish the anode's effective volumetric energy density and shelf life, while the air cathode's challenges include sluggish kinetics, low efficiency, and poor stability. Nevertheless, this Perspective highlights iron‐air MABs as an appealing sustainable alternative for grid‐scale energy storage, since iron is abundant and affordable, recyclable, has multielectron reversible redox activity, historically rich experience in production and processing, and is safe to handle. Given that further research will be directed to exploring the composition and design of electrolytes and electrodes, it may lead to advances in scaling and commercialization, as well as reducing the environmental impact of secondary batteries utilized for grid‐scale energy storage in the next decades.