Synthesis and characterization of Pt-doped LiFePO4/C composites using the sol–gel method as the cathode material in lithium-ion batteries

LiFePO4/C and LiFe0.96Pt0.04PO4/C nanocomposite cathode materials were synthesized using the sol–gel method in a nitrogen atmosphere. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Their electrochemical properties were investigated using galvanostatic charge/discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The XRD results indicate that substituting iron with platinum does not destroy the structure of LiFePO4, but expands the lattice parameters and enlarges the cell volume. The electrochemical results show that platinum doping improves the electrochemical performance of LiFePO4/C particles owing to the expansion of the lattice structure, which provides more space for Li ion diffusion. The, larger lattice structure parameters of the LiFe0.96Pt0.04PO4/C material result in a high discharge capacity of 166, 156, 142 and 140 mAh g−1 at rates of 0.2, 1, 5, and 10 C, respectively, as compared to 164, 150, 120, and 105 mAh g−1 for undoped LiFePO4/C.