Synthesis and Thermal Stability of LiCoO2

Lithium cobalt oxide, LiCoO2, was synthesized in air from a mixture of metallic cobalt and lithium carbonate powder and annealed at 850 to 1100°C to evaluate its thermal stability. Single-phase LiCoO2 was thermally stable at 850°C. The weight loss of samples at temperatures higher than 850°C and the presence of Co3O4 in the X-ray diffraction pattern at T > 900°C indicated the decomposition of LiCoO2. The time dependence of lithium oxide evaporation from LiCoO2 indicated that at 900°C the decomposition kinetics is controlled by LiCoO2 decomposition, while at T > 900°C the process is controlled by the diffusion of lithium ions in nonstoichiometric lithium cobalt oxide, LiyCo2-yO2, and in the CoO solid phase surrounding the particles. At T > 1000°C the formation of LixCo1-xO solid solution was also noted. Moreover, the decomposition rate seemed to depend on the temperature during the formation of lithium cobalt oxide.