Aqueous Fe-Based Batteries: From Fe-Metal Anode Reversibility to Electrolyte Stabilization and Cathode Expansion

Aqueous iron (Fe)-based batteries offer a compelling route toward sustainable stationary storage, yet their progress remains limited by an interdependent failure cascade involving the Fe-metal anode, electrolyte, and cathode. Recent progress is better understood through a sequential stabilization framework that links Fe-metal reversibility, electrolyte stabilization, and cathode expansion, rather than as a series of fragmented material challenges. At the core of this coupling, the fundamental limitations of the Fe anode, including nonuniform deposition and parasitic hydrogen evolution, are governed by electrolyte-defined boundary conditions, where Fe²⁺ solvation and water activity dictate interfacial kinetics. This systems-level perspective has broadened the cathode landscape from intercalation hosts to conversion and organic frameworks while underscoring the critical need to distinguish intrinsic cathode merits from performance gains enabled by upstream stabilization. By clarifying these crosscutting dependencies, this review outlines a strategic roadmap in which integrated full-cell evaluation and standardized benchmarking serve as key requirements for advancing durable, low-cost aqueous Fe-based energy storage.