Effect of Cobalt-Doped Electrolyte on the Electrochemical Performance of Lscfo/Cgo Interfaces

BAQUÉ, LAURA; PADMASREE, K.; CENICEROS REYES, M.; TROIANI, HORACIO; ARCE, MAURICIO; SERQUIS, ADRIANA C.; SOLDATI, ANALIA L.

San Diego

Congreso; ECS 229 - The Anual Meeting of the Electro-Chemical Society 2016; 2016

The Electrochemical Society

Solid oxide fuel cells (SOFCs) are efficient and environmental friendlydevices which directly convert hydrogen and fosil fuels into electric energy.The operation temperature of these devices is mainly determined by the natureof its electrolyte. Conventional SOFCs are composed of yttria basedelectrolytes requiring operation temperatures around 1000ºC, whereas ceriabased electrolytes have allowed reducing the temperature down to the 500-700ºCrange. Nevertheless, these materials require sinterization temperatures in the1300-1600ºC range to achieve complete densification, which produces very largegrain sizes and poor mechanical properties. In the last years, several researchworks have demonstrated that the addition of transition metals oxides iseffective in improving the densification and thus, lowering the sinterizationtemperatures of ceria based electrolytes. Such research works, generallyfocalize on how the addition of these sintering aids affect the properties(density, sintering temperature, conductivity) of the electrolyte. Nonetheless,it is well established that SOFC performance depends not only on thecharacteristics and performance of its individual components (i.e. cathode,electrolyte and anode) but also on their interfaces. Hence, a comprehensivestudy on how the addition of electrolyte sintering aids affects the cell performanceis still missing. In this work, we have studied La0.4Sr0.6Co0.8Fe0.2O3-d/Ce0.8Gd0.2O2-d/La0.4Sr0.6Co0.8Fe0.2O3-dsymmetrical cells containing Ce0.8Gd0.2O2-delectrolytes synthesized by a molten salt route [1] with and without Co oxidedoping. La0.4Sr0.6Co0.8Fe0.2O3-dnanostructured cathodes with high electrochemical performance [2,3] weredeposited by spin coating techniques on both sides of the electrolyte pellets.The assemblies were studied by Electrochemical Impedance Spectroscopy (EIS),X-Ray Diffraction and Transmission and Scanning Electron Microscopy. EISresults indicate that both electrolyte and cathode impedance response areaffected by the addition of the sintering aid to the electrolyte, despite usingcathodes with similar microstructure according to SEM observations. A possibleexplanation for such behavior was founded during TEM characterization whichreveals the formation of columnar structures at the cathode/electrolyteinterface of the cell with cobalt-doped electrolyte. These columnar structureswould negatively affect the cell performance hindering the diffusion of oxideions from the cathode to the electrolyte.