A detailed investigation was made into the production of high temperature lithium cobalt oxide (HT-LiCoO2) particles by continuous hydrothermal synthesis via the reaction of cobalt nitrate, lithium hydroxide, and hydrogen peroxide. The experiments were carried out in both subcritical and supercritical water, at temperatures ranging from 300 to 411 degrees C, with residence times less than 1 min in all instances. Although Co3O4 particles were synthesized in subcritical water at similar reaction conditions designed for comparison, well-ordered particles of HT-LiCoO2 were obtained in supercritical water. In supercritical conditions, the variations in temperature and residence time did not have significant impacts on the average particle size, particle size distribution, or morphology of obtained HT-LiCoO2. However, it was important to supply excessive lithium hydroxide and hydrogen peroxide in order to synthesize single-phased HT-LiCoO2 particles without undesired by-products. The hydrothermal synthetic route for LiCoO2, CoO, and Co3O4 in both subcritical and supercritical conditions was postulated. (C) 2009 Elsevier B.V. All rights reserved.