Conductivity of Lithium Salts in the Mixed Systems of High Permittivity Solvents and Low Viscosity Solvents

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Abstract
Electrolytic conductivities of LiClO4 and LiPF6 have been investigated in the mixed systems of the high permittivity solvents and low viscosity solvents. Propylene carbonate (PC), sulfolane (S), and dimethyl sulfoxide (DMSO) were used as the high permittivity solvents, and 1,2-dimethoxyethane (DME) and tetrahydrofuran (THF) as the low viscosity solvents. The conductivity of 1 mol dm−3 LiClO4 has a miximum in the mixed solvent with 40–80 m/o ether for every system. The conductance improvement by solvent-blending was qualitatively described in terms of a favorable combination of high permittivity and low viscosity of each component. The maximum conductivity of 1 mol dm−3 LiClO4 increased in the order of S<PC<DMSO for the systems containing THF. The difference in the order of maximum conductivity between DME and THF was interpreted by ion-solvent interactions, whose measure is generally expressed by the donor and acceptor properties of the solvent. The LiPF6 solutions had much higher conductance than those of LiClO4, especially in high DME concentration regions.