New counter electrode prepared as vanadium oxide and V/Ce oxide films: preparation and characterization

Vanadium oxide and mixed V/Ce-oxide films at 78, 55, 38, 32 atomic % of V were prepared via the sol-gel route from an aqueous colloidal solution of inorganic precursors. The influence of the added cerium precursor on their electrochemical, optical and structural properties was investigated by cyclic voltammetry (CV), X-ray analysis, LR spectroscopy and W-VIS techniques. The electrochemical stability of films was tested by CV measurements in 1 M LiClO(4) in propylene carbonate electrolyte. The addition of CeO(2) improved the poor stability of vanadium oxide films and enhanced their ion-charge capacity up to 30 mC/cm2 for thicknesses about 300 nm. The intercalation of Li(+) ions in vanadium oxide and V/Ce-oxide films was followed by FT-IR spectroscopy performed at near-grazing incidence angle (NGIA) conditions in combination with CV measurements at potentials of - 1.5 V and + 2.0 V (vs. Ag/AgCl). The observed shift of V-O(v) vibrations in the IR spectra confirmed the intercalation of Li(+) ions. (C) 1999 Elsevier Science B.V. All rights reserved.