Synthesis and electrochemical performance of LiV_3O_8/polythiophene composite as cathode materials for lithium ion batteries

摘要

LiV_3O_8/polythiophene (LiV_3O_8/PTh) composite has been chemically synthesized via an in-situ oxidative polymerization method. The structure and morphology of the samples have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). LiV_3O_8/PTh composite shows a single phase in the XRD pattern, but the existence of PTh has been confirmed by FTIR spectra. HRTEM images show that an uniform PTh layer with a thickness of 3-5 nm covered on the surface of LiV_3O_8. Electrochemical performance of samples has been characterized by the charge/discharge test, cyclic voltam-metry (CV), electrochemical impedance spectroscopic studies (EIS) and galvanostatic intermittent titration technique (CITT). The LiV_3O_8/PTh composite exhibits much better electrochemical performance than bare LiV_3O_8. The initial discharge capacities of 15 wt.% LiV_3O_8/PTh composite are 213.3 and 200.3 mAh g~(-1) with almost no capacity retention after 50 cycles at current densities of 300 and 900 mA g~(-1) respectively. PTh could enhance electronic conductivity, decrease the charge transfer resistance, increase the lithium diffusion coefficient, and thus improve cycling performance of LiV_3O_8. All these results demonstrate that the LiV_3O_8/PTh composite has a promising application as cathode material for lithium ion batteries.