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 drama tic effects on the structural and electrochemical characteristics of the co rresponding 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 modifi ed electrodes, prepared by using 1-year-old precursor solutions. The aging effects have also been evaluated from the systematic changes in the FTIR sp ectra, especially for the V=O and V-O-V vibrational peaks in the 1130-950 a nd 900-700 cm(-1) range, respectively. Based on light scattering measuremen ts, it has been shown that the polymerization of the polyvanadic acid precu rsor solutions does not stop even after 1 year. A condensation process take s place in parallel, leading to the formation of aggregates involving appro ximately four polymeric units. The polymerization and aggregation processes have been correlated with the changes in the X-ray diffraction and EIS pat terns, as well as with the changes in the electrochemical behavior of the V XG films before and after Li+ ion intercalation. (C) 2001 Elsevier Science Ltd. All rights reserved.