Ion conduction in solid electrolytes

Abstract

There is considerable technological interest in ion conducting solids for utilization in high energy and high power density battery and fuel cell systems and an intensive search is underway for materials with high conductivity for specific ions at low temperature. The majority of ionic crystals are insulators and exhibit small conductivity at temperatures appreciably below their melting point. A few solids, such as the silver halides and chalcogenides, the beta-alumina family of compounds, and mixed valence oxides with the fluorite arrangement, have exceptionally high ionic conductivity at relatively low temperatures (Fig. 1). This paper discusses the theoretical crystal-chemical and structural factors limiting high ionic conductivity in solids and problems hindering the discovery of superior new solid ionic conductors.