An integrated microstructural and electrochemical approach for cell-level modeling: the LSM-based Juelich cell

The typical weak point of existing SOFC cell-level models is the evaluation of the electrode effective properties, typically performed by using simple percolation models or by fitting the microstructural parameters on the polarization curves. In this study we present an integrated approach which incorporates a detailed microstructural modelling into the cell-level model. The three-dimensional microstructure of each porous layer is numerically reconstructed with packing algorithms for an accurate prediction of the effective properties [1]. The predicted effective properties are used in a two-dimensional electrochemical model, based on conservation equations written in continuum approach, describing transport and reaction phenomena within the cell. The integrated approach allows the prediction of the polarization behaviour from the knowledge of operating conditions and powder characteristics, eliminating the need for empirical correlations and adjusted parameters. The simulation of a short stack (F-design) of planar LSM-based anode-supported cells, developed and tested by Forschungszentrum Jülich, shows that a quantitative agreement with experimental data is obtained without fitting any parameter [2]. Simulations show that at 800°C the activation resistance in the cathode functional layer is the main contribution to cell overpotential. In addition, gas concentration effects at the anode produce the parabolic shape of the polarization curve near OCV and lead to reduce the polarization resistance as the water molar fraction in the fuel stream increases.