Computational Analysis of Performance Limiting Factors for the New Solid Oxide Iron-air Redox Battery Operated at 550 °C

In the present study, the effects of discharge and charge current densities, depth-of-discharge, initial porosity of Redox Cycle Unit (RCU), distance between Reversible Solid Oxide Fuel Cell (RSOFC) and RCU, and kinetic rate constant for the Fe3O4-reduction reaction on the electrochemical performance of a Solid Oxide Iron-Air Redox Battery (SOIARB) operated at 550 °C have been systematically investigated by a newly developed high-fidelity multi-physics model. The results show explicitly that the battery performance is kinetically limited by the Fe3O4-reduction during the charge cycle. The diffusion of Oxygen Shuttle Gas (OSG), i.e. H2-H2O, through the RCU pores and the gap between RSOFC and RCU is sufficiently fast. The most influential parameters on the performance are found to be the charge current density, depth-of-discharge and rate of Fe3O4 reduction. Strategies for design and operation of the SOIARB are subsequently developed with an aim to achieve a balanced energy capacity and cycle efficiency.