Materials for advanced high temperature secondary batteries

The materials problems and requirements in the development of advanced high temperature batteries are reviewed. The development effort on cells for these batteries has been focused on two major systems: sodium–sulphur cells, which use a solid electrolyte of β-alumina, and lithium–metal sulphide cells, which use a molten electrolyte of alkali halides (e.g. LiCl–KCl). In both systems, the severe corrosiveness of the cell active materials and the high temperature of operation place demanding restrictions on choice of materials of construction. The operating temperature is dictated by the ionic conductivity of the solid electrolyte and the melting point of the active materials for sodium–sulphur cells and the melting point of the electrolyte for lithium–metal sulphide cells. The materials of major concern in the sodium–sulphur cells are the β-alumina electrolyte, the positive electrode container/conductor, and the seal. In the lithium–metal sulphide cells, the major concerns are materials for the electrode separator and for positive electrode current collectors. In both systems, the need for components of low cost and light weight places further restrictions on materials selection.