A vibrational spectroscopic study of ion solvation and association in lithium perchlorate/gamma-butyrolactone electrolyte

The Raman and infrared (IR) spectra of gamma -butyrolactone (BL) containing various concentrations of LiClO4 have been measured and analyzed for the f irst time. It is found that both the vibrational frequencies and relative i ntensities of several BL bands change with increasing LiClO4 concentrations . The band splittings of the C-C stretch at 678 cm(-1) (both in Raman and I R) and of the C=O stretch at 1772 cm(-1) (in IR) show that there is a rathe r strong interaction between Li+ cation and BL molecule. This interaction o ccurs on the oxygen atom of the carbonyl of BL molecule. On the other hand, spectral curve fitting within the perchlorate band shape shows contributio ns of free ions and solvent separated ion pairs. Ion pairs as deduced by sp ectroscopic techniques provide a rational account for conductivity and visc osity of the electrolyte systems.