The preparation and electrochemical performances of LiFePO4-multiwalled nanotubes composite cathode materials for lithium ion batteries

LiFePO4-MWCNTs (multi-walled carbon nanotubes) composite cathode materials were prepared by mixing LiFePO4 and MWCNTs in ethanol followed by heat-treatment at 500 °C for 5 h. The structural, morphology and electrochemical performances of LiFePO4-MWCNTs composite materials were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), galvanostatic charge–discharge cycle tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicated that MWCNTs adding improved the electronic conductivity, the discharge capacity, cycle stability and lithium ion diffusion kinetics of LiFePO4, but MWCNTs adding did not charge the orthorhombic olivine-type structure of LiFePO4. In all these prepared LiFePO4 with x wt.% MWCNTs (x = 4, 7, 10) composites, 7 wt.% MWCNTs adding composite cathode shows the best electrochemical performance, which gets an initial discharge capacity of 152.7 mAh g−1 at 0.18 C discharge rates with capacity retention ratio of 97.77% after 100 cycles.