Proton-Mediated and Ir-Catalyzed Iron/Iron-Oxide Redox Kinetics for Enhanced Rechargeability and Durability of Solid Oxide Iron-Air Battery.

Long duration energy storage (LDES) is an economically attractive approach to accelerating clean renewable energy deployment. The newly emerged solid oxide iron-air battery (SOIAB) is intrinsically suited for LDES applications due to its excellent low-rate performance (high-capacity with high efficiency) and use of low-cost and sustainable materials. However, rechargeability and durability of SOIAB are critically limited by the slow kinetics in iron/iron-oxide redox couples. Here the use of combined proton-conducting BaZr Ce Y Yb O (BZC4YYb) and reduction-promoting catalyst Ir to address the kinetic issues, is reported. It is shown that, benefiting from the facilitated H diffusion and boosted FeO -reduction kinetics, the battery operated under 550 °C, 50% Fe-utilization and 0.2 C, exhibits a discharge specific energy density of 601.9 Wh kg -Fe with a round-trip efficiency (RTE) of 82.9% for 250 h of a cycle duration of 2.5 h. Under 500 °C, 50% Fe-utilization and 0.2 C, the same battery exhibits 520 Wh kg -Fe discharge energy density with an RTE of 61.8% for 500 h. This level of energy storage performance promises that SOIAB is a strong candidate for LDES applications.