Investigation on LiCoPO4 powders as cathode materials annealed under different atmospheres

An uncomplicated Pechini-assisted sol-gel process in aqueous solutions is used for the synthesis of Li-Co phosphate powders as cathode materials. The powders are annealed under different conditions in flowing nitrogen and in flowing air. The structural, morphological, and electrochemical properties are strongly dependent upon the annealing conditions. After the treatment in air, the X-ray diffraction (XRD) patterns reveal the presence of LiCoPO4 as a single phase. The morphology of the powders consists of a homogeneous and good interconnected blend of grains with different sizes; the cyclic voltammetry (CV) curves show a very good reversibility with very close values of the mean peak maxima in the cathodic region. The electrochemical measurements deliver a discharge specific capacity of 37 mAhg(-1) at a discharge rate of C/25 at room temperature. After annealing in nitrogen, the XRD analysis detects the formation of Li4P2O7 and to Co2P as secondary phases; the morphological investigation indicated that the LiCoPO4 particles took shape of prisms with an average size of 2 mu m. The CV curves are associated with a large polarization and poor irreversibility. The electrochemical measurements deliver a discharge specific capacity of 42 mAh g(-1) at a discharge rate of C/25 at room temperature and lower capacity fade (approx. 35%).