3D-Modelling and Performance Evaluation of Mixed Conducting (MIEC) Cathodes

Mixed electronic/ionic conducting (MIEC) cathode materials are qualified for the application in intermediate temperature SOFCs. The area specific resistance of MIEC cathodes is likewise determined by chemical composition and microstructure. A three-dimensional finite element method model, which is capable to analyze and predict the performance of MIEC cathodes, was developed. Representations for the actual cathode microstructure are automatically generated according to characteristic measures like cathode thickness, composition, porosity and average particle size. The model calculates the spatial distributions of the oxygen activity, the diffusive oxygen flux in the pores as well as the ionic current density inside the MIEC-cathode and inside the electrolyte material. Based on these values the area specific resistance of the cathode and the penetration depth of the ionic current can be evaluated. This paper will analyze the effect of surface-exchange k(0) and bulk diffusion coefficient D-0 as well as the influence of microstructure properties on the cathode performance.