Structural Analysis and Electrochemical Performance of Li2CoPO4F Cathode Materials

Li2CoPO4F cathode materials have been synthesized by a two-step method combining a sol-gel route and solid state reaction. X-ray diffraction (XRD) analysis confirmed that the Li2CoPO4F was well-crystallized in orthorhombic crystal structure with Pnma space group. From the high resolution transmission electron microscopy (HRTEM) image; the lattice fringes of {001} and {100} are well-resolved. HRTEM image and selected area electron diffraction (SAED) pattern reveal the highly crystalline nature of Li2CoPO4F having an ordered orthorhombic crystal structure. The Co atoms chains of Li2CoPO4F have been observed using high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The Raman and Fourier transform infrared spectroscopy (FTIR) spectra indicate the symmetry and stability of the Li2CoPO4F structure. The Li2CoPO4F cathode materials delivered an initial discharge capacity of 91 mAhg−1 at C/10 rate with good cyclic performance. The discharge profile of Li2CoPO4F shows a plateau at 5.0 V; revealing its importance as potentially high-voltage cathode.