Durability Testing of Solid Oxide Cell Electrodes with Current Switching

A method for durability testing of solid oxide cell electrodes in current-switching operation is presented. The aim is to obtain correlated time-dependent electrochemical and microstructural information by simultaneously testing multiple identical cells connected in series. By periodically removing cells from the circuit during the life test, microstructural changes were observed after different times under current using Focused Ion Beam-Scanning Electron Microscope (FIB-SEM) tomography. Initial tests were done on symmetrical cells with (La0.8Sr0.2)(0.98)MnO3 - Zr0.84Y0.16O2 (LSM-YSZ) electrodes at 800 degrees C in air with a current of up to 1.5 Acm(-2). The current direction was switched every 30 minutes. Electrochemical Impedance Spectroscopy (EIS) measurements showed stable operation at low currents, but a gradual degradation of both ohmic and polarization resistance at 1.5 Acm-2. Little microstructural change was observed except that silver from current collectors was found to migrate into the electrodes near the YSZ electrolyte during fuel cell operation. The silver content increased with time at current and presumably explained the observed increase in polarization resistance. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.008301jes] All rights reserved.