Influence of Working Parameters and Degradation on Anode-Supported Cells studied by Electrochemical Impedance Spectroscopy

Electrochemical Impedance Spectroscopy (EIS) is one of the most common techniques to characterize Solid Oxide Fuel Cells (SOFCs) during operation and to evaluate the influence on their performances of several working conditions and degradation effects. However, process overlapping in the frequency domain makes it difficult to clearly distinguish the contributions from each part of the cell to the impedance spectra. Therefore, a precise attribution of the electrodes losses and their evolution during the cell degradation becomes challenging. In this work a state of the art anode-supported cell [Ni/8YSZ-cermet anode, 8YSZ electrolyte with GDC interlayer, LSCF cathode] has been characterized by means of current-voltage curves and EIS under several working conditions. The impedance spectra have been analyzed calculating their distribution function of relaxation times (DRT) allowing to separate 4 different loss mechanisms occurring at the cell electrodes. The processes attribution has been carried out varying the feeding gases composition at Open Circuit Voltage (OCV) and under the electrical current load of 500mAcm-1 . Such procedure allowed to identify the the anode as the most affected cell component to the degradation after 100 hours of aging test under polarization.