Time-dependent performance changes in LSCF-infiltrated SOFC cathodes: The role of nano-particle coarsening

Symmetric solid oxide cells with Gd doped ceria (GDC) electrolytes and La0.6Sr0.4Co0.2Fe0.8O3 –δ (LSCF)-infiltrated-GDC cathodes were maintained in air with no current at temperatures from 650 to 850 °C. Comparison of SEM images before and after aging showed inhomogeneous coarsening of LSCF nano-particles in the cathodes. The polarization resistance, measured periodically at 600 °C using electrochemical impedance spectroscopy, increased at a higher rate with increasing aging temperature. The resistance variation was fit using a model that relates resistance to time-dependent LSCF surface area, based on surface diffusion limited coarsening. Good agreement with the experimental data is obtained for a limited range of fitting parameters. The model predicts that the cathode resistance should increase from ~ 0.2 to 0.28–0.35 Ω cm2, if maintained at the operating temperature of 600 °C for 40,000 h.

Research Highlights
► Accelerated testing method developed for infiltrated LSCF-GDC cathodes.
► Power law models for coarsening fit cathode performance variation.
► Prediction of cathode performance out to 40,000 h shows 40–70% degradation.
► SEM images indicate loss of LSCF surface area at high coarsening temperatures.