CONSIDERATIONS IN DESIGN AND CHARACTERIZATION OF SOLID-STATE ELECTROCHEMICAL SYSTEMS

The performance of a solid-state electrochemical system depends critically on the transport process in the bulk phases as well as the mass transfer and charge transfer across interfaces. The bulk transport process, such as diffusion under a chemical potential gradient and migration under an electric field, is relatively well-understood and property characterized. The phenomena occurring at an interface, however, have received little attention due either to the lack of understanding of these processes or to the experimental difficulty with determination of the interfacial properties. Although interfacial phenomena are far more complex in nature than bulk transport processes, their effect on the system performance is becoming more and more important, particularly for systems involving thin-film electrolytes or for operation at low temperatures. In both cases, the kinetics of interfacial processes dominate the performance characteristics. This paper addresses considerations in analysis and characterization of interfacial phenomena in solid-state electrochemical systems. The physical significance and characteristics of these processes are demonstrated in solid oxide fuel cells, oxygen sensors, and thermoelectric generators based on solid electrolytes. Furthermore, approaches to improve the interfacial properties and to optimize system performance are also illustrated.