An Intermediate-Temperature Solid Oxide Iron–Air Redox Battery Operated on O^2–-Chemistry and Loaded with Pd-Catalyzed Iron-Based Energy Storage Material

The solid oxide iron–air redox battery (SOIARB) operated on high-temperature O 2– -chemistry is an emerging all-solid-state battery suitable for large-scale energy storage with strong advantages in rate capacity and safety. However, it faces a serious challenge, particularly at lower temperatures, in rechargeability controlled by sluggish reduction kinetics of iron oxide. This work demonstrates that the slow iron oxide reduction kinetics can be significantly enhanced by loading Pd nanoparticles into the Fe-based energy storage material, achieving high cycle efficiency at high energy and power density. A representative result shows that at 500 °C and C /5.3 (10 mA cm –2, or 239.6 mA g –1 -Fe) rate, the battery delivers a discharge specific energy of 960.3 Wh kg –1 -Fe at 80% iron utilization ( U Fe ) and ∼600 Wh kg –1 -Fe at U Fe = 50% with an average cycle efficiency of 62.9% over 25 cycles.