Investigation of ion dynamics in LiClO4/EC/PC highly concentrated solutions by ionic conductivity and DSC measurements

Electrolyte conductivity and thermal properties of LiClO4 salt in mixtures of ethylene carbonate/propylene carbonate solvents, having fixed molar ratio EC46.5/PC19.0, have been measured over salt concentrations ranging from N=0.22 to N=1.01, where N is expressed as moles of salt divided by moles of solvent. In such a way, N=1.01 represents the saturation limit for this system. Both the measurements seem to confirm the findings of a previous study in which we reported about a “critical concentration value” (CCV) detected near the ratio N=[Li+]/[PC+EC]≅0.5. In fact, the sample having N approaching 0.5 has a quite peculiar conductimetric and thermal behaviour consistent with our previously reported hypothesis claiming the existence, close to this latter salt concentration value, of an ordered structure formed by Li+ cation sandwiched between two solvent molecules.