Improving thermal and electrochemical performances of LiCoO 2 cathode at high cut-off charge potentials by MF 3 (M=Ce, Al) coating

Abstract Surface coating of LiCoO 2 remained one of the efficient methods to enhance its electrochemical and thermal performances, especially at high cut-off potential. In this work, MF 3 (M = Ce, Al) coated LiCoO 2 was synthesized via co-precipitation method followed by a solid state reaction at 400 °C. The morphology and structure of the modified cathode material were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the fluoride compound MF 3 is successfully coated on the surface of LiCoO 2 cathode particles with an average layer thickness about 12 nm and 40 nm for AlF 3 and CeF 3 , respectively. The electrochemical tests show that the AlF 3 -coating layer significantly enhances the cycling performance of LiCoO 2 cathode material, even at high cut-off potential. While the bare LiCoO 2 cathode displays fast fading at 4.6 V vs. Li + /Li cutoff potential, the surface-modified electrode exhibits the great capacity of 160 mAh g −1 with excellent capacity retention on several cycles. We concluded that the electrochemical and the thermal enhancement at high potential are ascribed to the presence of MF 3 coating layer which prevent the side reaction during the charge discharge process, alleviate the attack by the acidic electrolyte and reduce the damage of electrode structure.