Connecting microstructural coarsening processes to electrochemical performance in solid oxide fuel cells: An integrated modeling approach

Abstract

In solid oxide fuel cells (SOFCs), Ni coarsening in porous anodes that are comprised of Ni and yttria stabilized zirconia (YSZ) leads to changes in several microstructural attributes, which affect the electrochemical performance. Herein we present an integrated modeling approach, where a dynamic mesoscale phase field model is linked with a stationary macroscale electrochemical cell level model in order to assess the role of Ni coarsening on the performance of SOFCs. The phase field model is capable of capturing the morphological evolution of Ni and accounting for its polycrystalline nature, while the electrochemical model encompasses the entire set of processes of gas transport, electronic and ionic conduction as well as the electrochemical reactions. Microstructural features are extracted from the phase field model as anode systems evolve over time and employed as effective properties in the electrochemical model. Simulation results highlight the importance of Ni and YSZ particle size and ratio on both the microstructural stability and electrochemical performance of SOFCs. In particular, it is shown that, for the classes of microstructures employed in this work, coarsening of Ni particles can either improve or diminish the maximum power density relative to the as-sintered ones, depending on the initial particle size.