Solid state synthesis of ultrafine-LiCoO2 by enhanced thermal decomposition of carbonate precursors followed by double-calcining

• Ultrafine HT-LiCoO2 was directly synthesized through thermal decomposition of carbonate.
• Ball milling can enhance thermal decomposition of the carbonate precursors.
• The nanometer LT-LiCoO2 can be obtained at 600 °C for 3 h.
• The nanometer LT-LiCoO2 transferred to the nanometer HT-LiCoO2 at 900 °C for 1 h.
• It shows good initial discharge capacity and cycle performance.

Ultrafine LiCoO2 powders with the layered rock-salt structure are successfully synthesized by enhanced thermal decomposition of carbonate precursors followed by double calcining. The mean size of the primary nanoparticles is about 500 nm with a narrow size distribution and is close to roundness with smooth surface. The LiCoO2 powders are also characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The lattice parameters of the synthesized LiCoO2 powders are the same as those of the corresponding powders formed by conventional high temperature solid-state synthesis processing. The double-calcining heating method can improve the crystalline perfection and produce the high temperature phase. The mechanism of solid-state reaction is also discussed. The electrochemical properties of as-formed ultrafine-sized LiCoO2 is examined and the maximum discharge capacities are 166.7 mAh/g, 160 mAh/g and 140 mAh/g at 0.2C, 0.5C and 1C, respectively. After 50 cycle performance, it is with a capacity retention of 88.84%, 88.10% and 72.90%, respectively.