Architected Iron-Carbon and Stainless-Steel Electrodes Fabricated by Additive Manufacturing for All-Iron Redox Flow Batteries

All-iron redox flow batteries are attractive candidates for large-scale energy storage owing to their use of earth-abundant and low-cost active materials. In this work, additively manufactured architected electrodes were developed to investigate the influence of electrode composition and architecture on cell performance. Stainless-steel electrodes were fabricated by laser powder bed fusion, while iron-containing carbon (Fe-C) electrodes were fabricated by digital light processing followed by carbonization. Gyroid and body-centered cubic (BCC) architectures were evaluated and benchmarked against commercial electrodes. Electrode composition was found to exert a greater influence on performance than architecture or electrode thickness. The Fe-C gyroid electrode achieved the highest peak power density (96.5 mW cm-2), outperforming both the stainless-steel gyroid electrode (74.2 mW cm-2) and commercial stainless-steel mesh (71.5 mW cm-2). Within the Fe-C electrode family, the gyroid architecture consistently outperformed the BCC structure, whereas only minor architectural effects were observed for the stainless-steel electrodes. Galvanostatic cycling further demonstrated stable long-term operation and distinct electrochemical behavior for the Fe-C electrodes, including unusually large first-discharge capacities and unique multi-step discharge profiles, suggesting the presence of additional electrochemically accessible iron species within the Fe-C framework. These results demonstrate the potential of combining additive manufacturing and resin engineering to create architected Fe-C electrodes for all-iron redox flow batteries. The distinct electrochemical behavior of the Fe-C electrodes, together with their superior polarization performance, suggests that architected iron-containing carbon electrodes represent a promising new electrode platform for iron-based flow battery systems.