Reconstruction and optimization of LSCF cathode microstructure based on Kinetic Monte Carlo method and Lattice Boltzmann method

Abstract

Solid phase sintering is a critical process for fabricating mixed ionic and electronic conductivity (MIEC) electrodes. In this study, the microstructures of MIEC electrodes are numerically reconstructed by a Kinetic Monte Carlo method. The performance of the reconstructed MIEC electrodes is then evaluated by a pore scale Lattice Boltzmann model. The present study provides the first comprehensive assessment of local O2 partial pressure on electrode performance. It is found that ohmic loss tends to play remarkable roles at a low O2 partial pressure of pO2<0.1bar. As insufficiency of O2 is almost unavoidable in the SOFC stack, the influence of local O2 partial pressure on ionic conductivity should be considered in LSCF modeling. Another important finding is that the initial states of compact powder have a profound impact on the electrode performance. Small initial grain size and irregular particles both contribute to generate large reaction area after sintering thereby decrease activation loss. It is also found that compact powder consistency even plays a more important role in electrode performance than particle size. The study also provides deep insight into influence of sintering process. The effective conductivity of electrode is mainly controlled by the enhancement of electrode connectivity. Subsequently, nanostructured SOFC electrodes by infiltration/impregnation are reconstructed evaluated numerically. The infiltrated electrodes demonstrate improved performance and significantly promote uniformity of reaction rates. The present study forms a solid foundation for optimization of the fabrication procedures to improve the fuel cell performance.