Hydrothermal synthesis of LiCoO2 for lithium rechargeable batteries

Ultrafine powders of LiCoO2 were prepared under mild hydrothermal conditions. Reactant mixtures of aqueous solutions of cobalt (II) nitrate, lithium hydroxide and hydrogen peroxide with different Co/Li and Co/H2O2 ratios were hydrothermally treated at 150–250 °C for 0.5–24 h in a Teflon-lined autoclave. Only HT-LiCoO2 phase was observed by X-ray diffraction (XRD) analysis. Scanning (SEM) and transmission (TEM) electron microscopies revealed the formation of well-crystallized hexagonal platelike particles with average size 70–200 nm. The increase in LiOH concentration results in better crystallinity. Annealing of hydrothermally prepared LiCoO2 at 230 °C leads to decreasing initial capacity from 130 down to 120 mA h/g, but improves cyclability (fade rate drops from 3.1 to 1.6 mA h/g per cycle). Submicrometric particle size and high surface area results in good electrochemical properties for high discharge rate.