Degradation of La0.6Sr0.4Fe0.8Co0.2O3-δ Oxygen Electrodes on Ce0.9Gd0.1O2-δ Electrolytes during Reversing Current Operation

In order to assess the durability of La0.6Sr0.4Co0.2Fe0.8O3 oxygen electrodes in reversible solid oxide cells, current switched similar to 1000 h galvanostatic (0.7, 1.0, and 1.5 A/cm(2)) life tests were performed on symmetrical Ce0.9Gd0.1O2-electrolyte cells at 700 degrees C. Cell operating voltage and resistance, the latter measured by impedance spectroscopy, were monitored throughout. Degradation was minimal for the 0.7 A/cm(2) case. For the higher current densities, the cell voltage and resistance increased with time, although the cell appeared to stabilize after similar to 500 h in the 1.5 A/cm(2) case. Post-test analyses showed no evidence of electrolyte cracking or delamination for any current. However, 3D imaging revealed measureable microstructural coarsening after 1.5 A/cm(2) operation that was not present after 0.7 A/cm(2) operation. Furthermore, the amount of Sr segregated onto LSCF surfaces was higher for the cells operated with current switching versus the as-prepared and zero-current cells. Analysis of the results suggest that much of the degradation was due to decreased oxygen surface exchange rate due to current-enhanced Sr segregation, with a smaller contribution due to microstructural coarsening. The possibility of extrapolating these accelerated tests to longer times is discussed. (C) The Author(s) 2017. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.