Li diffusion and electrochromism in amorphous and crystalline vanadium oxide thin film electrodes

• Autor(es):

  Scarminio, Jair (Universidade Estadual de Londrina. Departamento de Física);

  Catarini, Paulo R. (Universidade Estadual de Londrina. Departamento de Física);

  Urbano, Alexandre (Universidade Estadual de Londrina. Departamento de Física);

  Gelamo, Rogério V. (Universidade Estadual de Campinas. Instituto de Física Gleb Wataghin);

  Rouxinol, Francisco P. (Universidade Estadual de Campinas. Instituto de Física Gleb Wataghin);

  Moraes, Mário A. Bica de (Universidade Estadual de Campinas. Instituto de Física Gleb Wataghin).

• Fonte:

  Journal of the Brazilian Chemical Society; volume 19, número 4, páginas 788-794. 2008.

• Assuntos:

  vanadium oxide film;

  chronopotentiometric;

  DC measurements.

• Resumo:

  Amorphous vanadium oxide films were synthesized onto ITO-coated glass substrates by the hot filament metal oxide deposition technique. The as-deposited samples were heat-treated in an argon atmosphere. X-ray diffraction analysis revealed that the films treated at 200 and 300 ºC were still amorphous, while those treated at 400 and 500 ºC were crystalline, with a V2O5 structure. All electrodes were electrochemically reversible for Li+ intercalation, exhibiting the electrochromic effect, observed from optical transmittance measurements at 632.8 nm. The Li-diffusion coefficient, DC, was measured by the galvanostatic intermittent titration technique (GITT) as function of the inserted charge. For the crystalline films it was observed that the optical absorbance and the DC increase with increasing Li insertion in the single-phase regions of crystalline Li xV2O5 and decrease in the two-phase regions. For the latter, an effective DC was considered. The presence of other vanadium oxides mixed to the V2O5 matrix was inferred for the crystalline films from the chronopotentiometric and DC measurements.

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