Interface Contribution on Conductivity Enhancement in Doped Ceria−Carbonates Composite Electrolyte

Abstract

To simultaneously improve both ionic/electronic conduction in many electrochemical devices have received great attention. For example, (Ba,Sr)(Co,Fe)O3 perovskite exhibiting unique hole/oxygen ion mixed conduction behavior becomes important membrane materials for oxygen separation application. In additions, composite electrolytes consisting of multiple ionic conductors have received great attention for high temperature fuel cell application. For instance, enhanced conduction was observed when the oxygen ion conductor, doped ceria, was directly mixed with Li/K carbonates. The electrical conduction of composite electrolyte was contributed by the migration of oxygen ions in solid state and carbonate ions in liquid state. It is believed that ions tend to be highly mobile at the interface between doped ceria and carbonates. As a result, higher conductivity of the composite electrolyte was observed. In other words, the super-ionic conduction path/domain might exist at the interface between doped ceria and carbonates. However, to optimize the mixed conduction, the materials/microstructure designs play an important role. Thus, the objective of this study is to conduct (1) fabrication/design of composite electrolytes (2) microstructure development, (3) characterization of conduction/interfacial kinetics for composite electrolytes in high-temperature fuel cells. High-resolution SEM, XRD, and electrochemical Impedance Spectroscopy are employed to conduct microstructural, structural and impedance analyses. The electrical conduction behavior of composite electrolytes will be rationalized based on the pore size, pore distribution and interfacial area.