Temperature dependence of lithium ion solvation in ethylene carbonate–LiClO4 solutions

The solvation mechanism of lithium ions in pure ethylene carbonate (EC) solutions has been studied in a wide concentration range by different techniques and for temperatures up to 100 °C. For low concentrations (R=[Li+]/[EC]⩽0.1) the solvation number of Li+ cations in the solution has been found to be ∼7, by using nuclear magnetic resonance techniques. This number decreases at higher concentration, and complexes Li+-EC with ∼3 solvent molecules per cation are formed when R=0.33. The temperature dependence of the solvation has been investigated for the more concentrated solutions by Raman spectroscopy. When the temperature increases, the relative intensity of the Raman bands upshifted by the lithium interaction also increases remarkably, indicating that Li+ ions form complexes with a higher solvation number. On the other hand, a higher degree of reassociation of Li+ cations with perchlorate anions is observed.