Lithium electroinsertion into an inorganic-organic hybrid material composed from V₂O₅ and polyaniline

Composites of V₂O₅ xerogel with polyaniline (PANI) are prepared from a vanadyl tris(isopropoxide) precursor and aniline monomer by in situ oxidative polymerization of aniline in the sol solution, followed by gelation with the inorganic oxide. The composite is characterized using Fourier transform infrared spectroscopy, X-ray diffraction, electroacoustic impedance, electrochemical quartz crystal microbalance (EQCM), electrochemical impedance, in situ resistance, cyclic voltammetry, UV-visible (UV-vis) spectroscopy, and multiple charge/discharge measurements. Electrochemical impedance data at -0.7 V give a value for the Li⁺ diffusion coefficient in the composite of 2 × 10^-11 cm² s^-1, in contrast to the value of 3 × 10^-12 cm² s^-1 obtained for V₂O₅. EQCM data show that charge compensation in the composite is achieved predominantly by Li⁺ electromigration, as is also the case for V₂O₅. In situ resistance measurements reveal that the composite has a very high conductivity over the potential range 0.4 to -0.5 V. In contrast, V₂O₅ exhibits much lower conductivity over this range and also shows a deep minimum in conductivity near -0.2 V. Both materials become more resistive at potentials more negative than -0.5 V. UV-vis spectroscopy of the materials reveals changes in the optical bandgap that are consistent with these resistance changes. Finally, the composite shows excellent stability toward repeated charge/discharge cycling.