Exploring iron-containing electrodes for all-iron redox flow batteries

This work investigates the use of iron- and steel-based electrodes as alternatives to prevalent carbon fiber-based electrodes in the negative half-cell of all-iron redox flow batteries. Through electrochemical and structural characterization of planar electrodes, we demonstrate that stainless steel, particularly the 316-type, enables improved iron plating kinetics and comparable or superior performance in flow cell configurations. Three-dimensional porous architectures were evaluated, revealing that mesh structures offer high permeability and stable cycling, while non-woven mats provide higher gravimetric capacity but are susceptible to pore clogging and mass transport limitations. Full-cell tests confirm enhanced voltage efficiency and capacity retention for steel-based electrodes over state-of-the-art carbon materials, as they limit oxide precipitation and electrode clogging. The results highlight the critical role of electrode microstructure and surface chemistry in phase-evolving systems and highlight the potential of steel electrodes as scalable, cost-effective alternatives for next-generation hybrid flow battery applications.