Comparison of the Degradation of the Polarization Resistance of Symmetrical LSM-YSZ Cells with Anode Supported Ni-YSZ/YSZ/LSM-YSZ SOFCs

Impedance spectra of a symmetrical cell with SOFC cathodes (LSM-YSZ/YSZ/LSM-YSZ) and an anode supported planar SOFC (Ni-YSZ/YSZ/LSM-YSZ) were collected at OCV at 650 degrees C in air (cathode) and humidified (4%) hydrogen (anode), over 155 hours. The impedance was affected by degradation over time in the same frequency range for both cells (similar to 10 Hz), possibly indicating that the same physical process was affected in both types of cell. However, deconvolution of the impedance data was not straightforward. When n-values of the constant phase elements in the otherwise identical equivalent circuit for the full cell were changed slightly, very different results were obtained, showing the high sensitivity of the fitting procedure. Therefore, the equivalent circuit applied should be refined further, requiring comparison of impedance data of the cells at higher temperature (750, 850 degrees C).