IONIC-CONDUCTIVITY OF LI2O-BASED MIXED OXIDES AND THE EFFECTS OF MOISTURE AND LIOH ON THEIR ELECTRICAL AND STRUCTURAL-PROPERTIES

Thermal, structural, and electrical measurements on polycrystalline Li2O and certain Li20-based mixed oxides [Li5MO4M = Al, Fe, and Ga), Li2O + ZnO, LiYO2, and Li2O + Y2O3 mixtures] indicate that LiOH is produced within these materials on exposure to a moist environment. The presence of LiOH produces an endothermic reaction at ~400°C and a large increase in ionic conductivity above ~400'C [ 0.1 (-cm)-1 at 500°C]. These features are absent under dry conditions (no LiOH). In the dry state, the ionic conductivity varies nearly exponentially with temperature (activation energies of ~0.5-1.0 eV) and has values ranging from 10-4 to 10-3 (-cm) -1 at 500-C. All of these materials, except possibly for the Y-containing compounds, appear to have common ionic conductivity characteristics. The electrical and structural properties of the Li5MO4 compounds are reproducible on cycling between wet (containing LiOH) and dry (no LiOH) conditions. This does not appear to be the case for the other materials. There is a significant (1-50%) electronic contribution to the conductivity in these materials. © 1979, The Electrochemical Society, Inc. All rights reserved.