Chemical synthesis and properties of spinel Li1-xCo2O4-delta

Spinet Li1-xCO2O4-delta samples with 0.44less than or equal to(1-x)less than or equal to1 have been synthesized by chemically extracting lithium with the oxidizer NO2BF4 in acetortitrile medium from the LT-LiCoO2 synthesized at 400degreesC. Rietveld analysis of the X-ray diffraction data reveals that the Li1-xCO2O4-delta samples adopt the normal cubic spinet structure with a cation distribution of (Li1-x)(8a)[CO2](16d)O4-delta. Redox iodometric titration data indicate that the LT-LiCoO2 tends to lose oxygen on extracting lithium and the spinet Li1-xCO2O4-delta samples are oxygen-deficient. Both infrared spectroscopic and magnetic susceptibility data suggest that the LiCo2O4-delta spinet is metallic with itinerant electrons. The tendency to lose oxygen on extracting lithium from the LTLiCoO2 and the observed metallic behavior of the spinet LiCO2O4-delta are explained on the basis of a qualitative band diagram. (C) 2002 Elsevier Science (USA).