Enhanced electrochemical performance of LiFePO4 of cathode materials for lithium-ion batteries synthesized by surfactant-assisted solvothermal method

Lithium iron phosphate (LiFePO4) cathode materials were synthesized by the solvothermal method with the assistance of different surfactants. The influences of polyethylene glycol 2000 (PEG 2000), polyvinylpyrrolidone (PVP), and cetyltrimethyl ammonium bromide (CTAB) on the microstructure and electrochemical performance of LiFePO4 were investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), electrochemical impedance spectroscopy (EIS), and charge/discharge measurements. The particle size of the LiFePO4 synthesized with the assistance of PEG was uniform and showed a flat rhombohedron-like shape. The initial discharge specific capacity is up to 122.80 mAh/g with an initial coulombic efficiency of 95.50% at 0.1C. LiFePO4 synthesized with PVP-assisted presents a porous structure with an initial discharge specific capacity of 91.01 mAh/g. LiFePO4 synthesized with CTAB-assisted shows a flower-like morphology with an initial discharge specific capacity of 100.44 mAh/g. Though the initial discharge capacities of the LiFePO4 materials prepared with the assistance of CTAB and PVP are lower than those of the LiFePO4 prepared without the assistance of surfactant, the two materials exhibited excellent cyclic stability at 0.1C.