| Abstract Scope |
Iron is earth-abundant, low-cost, with significant potential for sustainable grid-scale energy storage. However, electrochemical performance of alkaline Fe-based batteries is often limited by surface passivation, interfacial phase evolution, and morphological degradation during cycling. In alkaline Fe–S electrodeposition processes, sulfur-containing species further influence interfacial reactions, leading to complex surface chemistry that remains poorly understood. We investigated formation and evolution of Fe–S interphase by correlating electrochemical performance with changes in electrode morphology and surface composition. Cycling performance is combined with ex situ electron microscopy and surface characterization to identify reaction products and monitor structural evolution throughout cycling. Particular attention is given to formation, stability, and electrochemical role of sulfur-containing surface species and their impact on passivation, redox reversibility, and long-term cycling stability. The results provide mechanistic insights into interphase evolution in alkaline Fe–S redox systems and establish design principles for engineering stable electrode interfaces to enable durable, low-cost iron-based energy storage systems. |