(799b) Complex Metal Oxide Nanowires for Thermoelectric and Battery Applications

Complex metal oxides are unique type of materials where they can be used for both energy generation and storage. The stability of the oxides at high temperatures, low toxicity and cost, and chemical stability make them very attractive candidates for commercial applications. In thermoelectrics, complex metal oxide-based materials have faced drawbacks in having high thermal conductivity and low power factor, in turn affecting the thermoelectric figure of merit (ZT). Hence, research was never heavily concentrated on oxides. Our approach to solving the problem of their high thermal conductivity and low power factor has been through nanostructuring, where the three important properties - thermal conductivity, electrical conductivity and Seebeck coefficient become quasi-independent of each other. We have researched on a unique of phase of calcium cobalt oxide (Ca₉Co₁₂O₂₈), which is a layered oxide. This phase has hardly been researched in literature because of its high thermal conductivity, thus limiting its use in thermoelectric devices. Through a unique single source precursor based technique, we have been able to synthesize porous nanowire structures of Ca₉Co₁₂O₂₈ at temperatures much lower than conventional solid state techniques. Significantly improved ZT has been observed in our nanowire system up to 700K due to reduced thermal conductivity and enhanced Seebeck coefficient compared to the literatures. Same synthetic approach has also been used to prepare porous nanowires of lithium cobalt oxide (LiCoO₂). The battery electrode based on these porous nanowires showed the capability to maintain their rate capabilities and accelerated Lithium ion diffusion compared to micron sized particles for high energy demanding.