Iconic conductors for solid state battery systems

In this project, it has been demonstrated that cuprous iodide -sulph.onium iodide double salts, similar to the silver iodide systems previously studied by other workers, are suitable for use in ambient temperature batteries for low current applications. A number of potential solid electrolytes, in which the mobile species is calcium, have also been investigated, and areas for further work have been defined. The relavent section of the thesis is confidential as patent proceedings are possible. The project has involved not only a search for new electrolytes, but also the development of a search strategy. In view of the limitations of direct conductivity measurements on compacted materials, arising from electrical contact problems, considerable use has been made of indirect methods. A critical review of standard electrochemical techniques, often adapted from aqueous methods, has been carried out. This has highlighted shortcomings in the measurements of such para.meters as electronic conductivity, where the self-discharge rate, a pare.meter used by battery technologists, has been found more meaningful than the results obtained from Wagners blocking electrode technique. X-ray diffraction (XRD), and differential thermal analysis (DTA) have been used to disprove the common assertion that the effect of addition of organic dopant materials to silver iodide ha.s the effect of stabilizing the high temperature high conductivity alpha phase. CuI based electrolytes have been found to differ significantly from the AgI analogues in several respects. No simple structural criterion, such as the Group Weighting Coefficient for AgI systems, could be found to predict the effect of addition of organic sulphonium iodide dopants. Battery cells based on Cul did not give the expected thermodynamic open circuit voltage (OCV), and three electrode measurements failed to elucidate this anomaly. The possible involvement of the cupric ion was explored in several ways, including the first application of Auger electron spectroscopy for this type of electrolyte system. The battery discharge characteristics showed a fairly low efficiency, but indirect evidence including the inadvertent involvement of a novel solid state aurous system, pointed to the majority of the anode material being unavailable for reaction.