Electrochemical Performance of LiV3O8/PPy Composite Materials Synthesized by the Non-water System

LiV3O8/polypyrrole (PPy) composite materials were prepared by an oxidative polymerization of pyrrole monomer on the surface of LiV3O8 using ethanol as a medium, FeCl3 as an oxidant, benzene sulfonic acid sodium salt as a dopant. The crystal structures and microstructures of LiV3O8/PPy were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The electrochemical properties of the composites were investigated with galvanostatic charge-discharge test, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that 10 nm pyrrole is uniformly polymerized around the LiV3O8, and the PPy-coating does not alter the crystal structure of the LiV3O8. LiV3O8/PPy composite material containing 6% PPy (LVP6) exhibits perfect electrochemical properties, whose first discharge capacity reaches a high specific discharge capacity of 274 mAh/g and maintains a stable capacity of 239.4 mAh/g within 100 cycles at the charge-discharge rate of 0.1 C and in the voltage range of 1.8 similar to 4.0 V, and the capacity retention is 87.4%. But the pure LiV3O8 shows that the first discharge capacity is 227.4 mAh/g and the discharge capacity is 160.1 mAh/g after 100 cycles, the capacity retention is only about 70.4%. LiV3O8/PPy composite materials exhibit better cycling performance than the pure LiV3O8.