In Situ Induced Interface Engineering in Hierarchical Fe₃O₄ Enhances Performance for Alkaline Solid-State Energy Storage

Rechargeable aqueous batteries adopting Fe-based materials are attracting widespread attention by virtue of high-safety and low-cost. However, the present Fe-based anodes suffer from low electronic/ionic conductivity and unsatisfactory comprehensive performance, which greatly restrict their practicability. Concerning the principle of physical chemistry, fabricating electrodes that could simultaneously achieve ideal thermodynamics and fast kinetics is a promising issue. Herein, hierarchical Fe₃O₄@Fe foam electrode with enhanced interface/grain boundary engineering is fabricated through an in situ self-regulated strategy. The electrode achieves ultrahigh areal capacity of 31.45 mA h cm^-2 (50 mA cm^-2), good scale application potential (742.54 mA h for 25 cm² electrode), satisfied antifluctuation capability, and excellent cycling stability. In/ex situ characterizations further validate the desired thermodynamic and kinetic properties of the electrode endowed with accurate interface regulation, which accounts for salient electrochemical reversibility in a two-stage phase transition and slight energy loss. This work offers a suitable strategy in designing high-performance Fe-based electrodes with comprehensive inherent characteristics for high-safety large-scale energy storage.