Characterization and electrochemical performances of MoO_2 modified LiFePO_4/C cathode materials synthesized by in situ synthesis method

摘要

The MoO_2 modified LiFePO_4/C cathode materials were synthesized by in situ synthesis method. Phase compositions and microstructures of the products were characterized by X-ray powder diffraction (XRD), SEM, TEM and EDS. Results indicate that MoO_2 can sufficiently coat on the LiFePO_4 surface and does not alter LiFePO_4 crystal structure, the existence of MoO_2 decreases the particles size and increases the tap density of cathode materials. The electrochemical behavior of cathode materials was analyzed using galvanostatic measurement, cyclic voltammetiy (CV) and electrochemical impedance spectroscopy (EIS). The results show that the existence of MoO_2 improves electrochemical performance of LiFePO_4 cathode materials in specific capability and lithium ion diffusion and charge transfer resistance. The initial charge-discharge specific capacity and apparent lithium ion diffusion coefficient increase, the charge transfer resistance decreases with MoO_2 content and maximizes around the MoO_2 content is 5 wt%. It has been had further proved that the MoO_2 adding enhances the electronic conductivity and lithium ion transport to improve the electrochemical performance of LiFePO_4 cathode materials.