Disordered carbon nanofibers/LiCoPO4 composites as cathode materials for lithium ion batteries

LiCoPO4-coated disordered carbon nanofibers (CNFs/LiCoPO4) were obtained by a sol-gel method, using triethyl phosphite or triethyl phosphate as the phosphorous source. The crystal structure of the products was analyzed by X-ray powder diffraction, while morphology was studied using scanning electron microscopy, transmission electron microscopy, Auger electron spectroscopy and X-ray photoelectron spectroscopy. Optimal synthesis conditions for the CNFs/LiCoPO4 in light of the best electrochemical performance are discussed. The best discharge capacity 105 mAh/g (or ca. 63% of the theoretical capacity) shows the material with 40% CNFs/LiCoPO4 and addition coating by carbon black. This composition has a best purity of active materials and point coverage of CNFs. The X-ray photoelectron C1s spectra of the CNFs surface without and with sputter erosion show enhancement of C-O bonds at the fiber surface, which does not influence significantly electrochemical behavior of the composite materials.