In this work we used IR spectroscopy as an analytical tool to estimate the degree of Li+ intercalation in crystalline V2O5 films. Films were prepared from a V-oxoisopropoxide precursor, using a sol-gel mute. After the deposition of the films by dip-coating, the films were heated at 300 degrees C for 60 min. A polaron absorption extending from the visible and near IR and terminating at 2000 cm(-1) was observed in insitu FT-IR reflection-absorption (LO modes) and ex-situ FT-IR absorbance (TO) spectra of V2O5 films. Results showed that the intensity of the polaron absorption depends on the amount of intercalated Li+ ions and therefore the applied potential. The variation in the intensity of the polaron absorption was accompanied by the reversible changes of the TO and LO vibrational modes in the ex-situ and in-situ IR spectra of V2O5 films.