Lithium Hydride Cell Studies: Conductivity of Lithium Hydride-Lithium Halide Electrolytes

The search for an electrolyte suitable for use in a lithium hydride emf cell has fostered investigations of the lithium hydride-lithium halide (Cl^-, Br^-, I^-) binary fused salt systems. Temperature-composition data obtained for these systems showed that each has a simple eutectic (see ANL-7125, p. 203). Using the solid-liquid equilibrium temperature data, calculations were made of the excess chemical potential for each component of the binary system. These calculations indicate that all systems show positive deviations from ideality for the lithium hydride component of the electrolyte. These positive deviations can be totally accounted for by assuming that the system is made up of dimeric lithium halide (Li₂X₂) species and lithium hydride monomer.3 Indications of dimeric lithium halide species have also been obtained from interpretations of the freezing point depression of lithium hydride by the lithium halides.3 If such associated species are present in the electrolyte, a significant change in the normal ionic character of the electrolyte might result. In an attempt to elucidate further the nature of the species in these fused salt solutions, electrical conductance measurements are being made.