Electrochemical performance of LiV3O8/PPy composite materials synthesized by the non-water system

Abstract:

LiV₃O₈/polypyrrole (PPy) composite materials were prepared by an oxidative polymerization of pyrrole monomer on the surface of LiV₃O₈ using ethanol as medium, FeCl₃ as oxidant, benzene sulfonic acid sodium salt as 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 show that 10nm pyrrole was uniformly polymerized around the LiV₃O₈, and the PPy-coating did not alter the crystal structure of the LiV₃O₈. LiV₃O₈/PPy composite material containing 6% PPy (LVP6) exhibits perfect electrochemical properties, its 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 1.8～4.0 V, 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 show better cycling performance than the pure LiV₃O₈.

Key words:LiV₃O₈; polypyrrole; coating; cathode material