Long-term aging of vanadium(V) oxide xerogel precursor solutions: structural and electrochemical implications

Long-term aging of polyvanadic acid precursor solutions gives rise to dramatic effects on the structural and electrochemical characteristics of the corresponding V2O5. nH(2)O xerogel products. Among these, an 880 mV shift of the redox waves has been observed in the cyclic voltammograms of the modified electrodes, prepared by using 1-year-old precursor solutions. The aging effects have also been evaluated from the systematic changes in the FTIR spectra, especially for the V=O and V-O-V vibrational peaks in the 1130-950 and 900-700 cm(-1) range, respectively. Based on light scattering measurements, it has been shown that the polymerization of the polyvanadic acid precursor solutions does not stop even after 1 year. A condensation process takes place in parallel, leading to the formation of aggregates involving approximately four polymeric units. The polymerization and aggregation processes have been correlated with the changes in the X-ray diffraction and EIS patterns, as well as with the changes in the electrochemical behavior of the VXG films before and after Li+ ion intercalation. (C) 2001 Elsevier Science Ltd. All rights reserved.