Syntheses of LiCoO2 for cathode materials of secondary batteries from reflux reactions at 130–200 °C

Low temperature syntheses of LiCoO2 cathode materials for Li-secondary battery applications were studied in aqueous solutions by hydrothermal and reflux reactions. By controlling the oxidation potential of the reaction environments, we could synthesize phase pure LiCoO2 directly from Co(OH)2 at as low as 130 °C, contrary to the reported hydrothermal reactions at 200–220 °C starting with CoOOH. Having high pH over 15 and an O2 flow induced the oxidation reaction of the divalent cobalt in Co(OH)2. The products so obtained have well-crystallized high temperature form of LiCoO2 with the layered structure as proved by powder X-ray diffraction (XRD) and the Raman spectroscopy data. The particles have a uniform size distribution around 100 nm with well-developed crystallite morphology.