La0.6Sr0.4CoO3−δ modified LiFePO4/C composite cathodes with improved electrochemical performances

LiFePO4/C particles were coated with highly conductive La0.6Sr0.4CoO3−δ (LSC) via a suspension mixing method followed by heat-treating. The effects of LSC coating were studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), galvanostatic charge/discharge test, electrochemical impedance spectroscopy (EIS), potential step chronoamperometry (PSCA) and cyclic voltammetry (CV). The results of HRTEM and XRD showed that the incomplete carbon network could be repaired by nanometer-sized LSC while the co-coated composite retained the structure of LiFePO4. Electrochemical test results indicated that LSC coating could significantly improve the electrochemical performances at high charge/discharge rates. The 4 wt.% LSC-coated LiFePO4/C sample exhibited the best electrochemical performance with discharge capacities of 136, 125 and 96 mAh g−1 at the rates of 1, 2 and 5 C, respectively. These data were much higher than those of the uncoated sample. This improvement could be mainly attributed to the lower charge transfer resistance and higher diffusion coefficients of Li+ ions resulted from the higher conductivity of LSC and the faster kinetic process between the LSC/LiFePO4 interfaces.

► Highly conductive La0.6Sr0.4CoO3−δ was coated on the surface of LiFePO4/C. ► Coated cathodes showed significant improved rate performance and cycle performance. ► The LiFePO4/C sample coated with 4 wt.% La0.6Sr0.4CoO3−δ delivered a maximum discharge capacity of 96 mAh g−1 at 5 C compared with 65 mAh g−1 for the pristine LiFePO4/C sample. ► La0.6Sr0.4CoO3−δ coating increases charge transfer reaction activity and prevents LiFePO4 particles from contacting electrolyte directly.