LI-PROPYLENE CARBONATE CONCENTRATED-SOLUTIONS - A COMPREHENSIVE MODEL( SOLVATION IN ETHYLENE CARBONATE)

Spectroscopic (Raman, NMR, impedance spectroscopy), and thermal [diffe rential scanning calorimetry (DSC)] techniques have been used to study the solvation mechanism of lithium ions in ethylene carbonate (EC)-pr opylene carbonate (PC) concentrated solutions. For values of N = [Li+] /[EC + PC]less than or equal to 0.2 all the cations are solvated. by s imilar to 4 solvent molecules and interaction chiefly takes place betw een Li+ and the ring oxygens, For N>0.2 a part of Li+ ions begins to f arm complexes with two solvent molecules (sandwich configuration). At N congruent to 0.5 nearly all cations are complexed, and a crystalline compound is formed at room temperature. For higher values of N a reas sociation of the salt takes place. (C) 1997 American Institute of Phys ics.