Microstructure optimization of porous mixed ionic and electronic conducting cathode for solid oxide fuel cells

Abstract

In the present study, a numerical method is proposed to optimize the porous mixed ionic and electronic conducting (MIEC) cathode microstructure of the solid oxide fuel cell (SOFC). During the optimization, the local non-uniform three-dimensional distributions of solid and pore phases are deformed so that the total amount of reaction current is maximized. Computational results show that the total reaction current in the optimal La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathode microstructure increased by 40% compared with that of the original real structure reconstructed from the focused ion beam scanning electronic microscope (FIB-SEM). Different initial structures are applied for the optimization, where the difference in the optimized total reaction currents between different initial microstructures are less than 4%. Universal optimal geometric features are extracted from these optimizations, i.e. the microstructures are composed of small particles, and the solid volume fraction reduces monotonically from the electrolyte along the thickness direction. Then, the influence of the grid size on the optimization is analyzed. Finally, the influence of the bulk ionic conductivity on the optimization is investigated. For the cathode with higher bulk ionic conductivity, the reactive thickness is thinner and the solid volume fraction is smaller, which results in more pronounced performance improvement.