An investigation of V2O5/polypyrrole composite cathode materials for lithium-ion batteries synthesized by sol–gel

A lamellar compound of V2O5 was prepared by a simple sol–gel method using H2O2 and V2O5 as starting materials. The composites of V2O5/PPy (polypyrrole) were synthesized by in situ polymerization, and characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrum, and X-ray diffraction (XRD). The electrochemical properties of the composites were investigated with galvanostatic charge–discharge test, cyclic voltammetry and A.C. impedance techniques. The results show that pyrrole was uniformly polymerized around the V2O5, and the V2O5/PPy composite possessed excellent electrochemical performance. The specific discharge capacity of the 2.5% mass percent PPy composites (271.8 mAh g−1) was higher than that of pure V2O5 (247.6 mAh g−1) at 0.1C rate and it has the voltage limits of 1.8–4.0 V. Furthermore, the specific discharge capacity remained at 225.4 mAh g−1 after 50 cycles. The chemical diffusion coefficient D Li + values were calculated, depending on x-values in Lix+1.1V2O5. The values of D Li + range from 2.18 × 10−12 cm2 s−1 to 4.5 × 10−14 cm2 s−1 for V2O5/PPy composite, and it decreased as the amount of intercalated Li+ increased.