Fundamental aspects of noble metal doped LiFePO4 cathode for Li-ion batteries applications.

摘要

LiFePCVC and LiFe_(0.96)Pt_(0.04)PO4/C nano composite cathode materials were synthesized using the sol-gel method in a nitrogen atmosphere. 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 LiFePCVC particles owing to the expansion of the lattice structure, which provides more space for Li ion diffusion. The, larger lattice structure parameters of the LiFe_(0.96)Pt_(0.04)PO4/C material result in a high discharge capacity of 139 mAh g~(-1) at rates of 10 C, as compared to 105 mAh g~(-1) for undoped LiFePCVC LiFePO4 and LiFe_(0.96)Pt_(0.04)PO4/C composites were also synthesized using hydrothermal method. The XPS results indicated that platinum doping does not change the chemical state of Fe (II). The SEM and BET results showed that platinum doping reduces the size of the particles. The electrochemical characterization of the electrodes using discharge capacity, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) showed that the Li-ion cell based on LiFe_(0.96)Pt_(0.04)PO4/C elecrode exhibited better charge /discharge performance than those of LiFeP04/C sample.