chemical Synthesis and Properties of Spinel Li1-xCo2O4delta

Spinel Li1-xCo2O4-delta samples with 0.44< or =(1-x)< or =1 have been synthesized by chemically extracting lithium with the oxidizer NO2BF4 in acetonitrile medium from the LT-LiCoO2 synthesized at 400°C. Rietveld analysis of the X-ray diffraction data reveals that the Li1-xCo2O4-delta samples adopt the normal cubic spinel structure with a cation distribution of (Li1-x)8a[Co2] 16dO4-delta. Redox iodometric titration data indicate that the LT-LiCoO2 tends to lose oxygen on extracting lithium and the spinel Li1-xCo2O4-delta samples are oxygen-deficient. Both infrared spectroscopic and magnetic susceptibility data suggest that the LiCo2O4-delta spinel is metallic with itinerant electrons. The tendency to lose oxygen on extracting lithium from the LTLiCoO2 and the observed metallic behavior of the spinel LiCo2O4-delta are explained on the basis of a qualitative band diagram.