For solid oxide fuel cell (SOFC) systems to become economically competitive, continuous development of new materials and processes is required not only to enhance SOFCs durability but also to reduce their cost. The cathode electrode is known to contribute the most to SOFC performance degradation and efficiency loss. In the case of strontium doped lanthanum cobalt iron oxide, it has been frequently suggested that strontium migration to the cathode surface under operating conditions plays an important role in the degradation. Recently, there have been extensive efforts to modify the surface of the cathode in order to improve the reliability. Most of these attempts have been focused on surface modification subsequent to the cell fabrication (e.g. infiltration). An attractive alternative is to modify the cathode powder surface prior to incorporating the powder into the SOFC. This approach would simplify the manufacturing flow, allowing a “drop-in replacement” of existing cathode powders, while potentially providing similar or even better performance enhancements.

In this work, commercial (La_0.6Sr_0.4)_0.95Co_0.2Fe_0.8O_3-d (LSCF) powders have been modified by atomic layer deposition (ALD) using zirconia-, ceria- and hafnia-based oxides. The effect of coating thickness (number of ALD cycles) and dopant addition have been investigated. Morphology and porosity of sintered samples based on ALD coated powders and the pristine powder were found to be rather similar. On the other hand, the electrochemical performance of cathodes based on the ALD treated powders was significantly different from that of the unmodified cathode. This paper examines the details of electrochemical behavior of ALD modified and unmodified powders. Electrochemical impedance spectroscopy (EIS) analysis of symmetrical cells under air at 600-800 °C temperature range showed that high and medium frequency arcs were highly affected in ALD treated samples whereas the low frequency region stayed unchanged. The effect of surface modification of LSCF powders on durability of the LSCF-based cathode is under comprehensive assessment.