Mobility and Ionic Association of Lithium Salts in a Propylene Carbonate‐Ethyl Methyl Carbonate Mixed Solvent

Abstract

Electrolytic onductivities of lithium salts have been measured in equimolar mixtures of pr_o~vlene carbonate and either ethyl methyl carbonate or 1,2-dimethoxyethane t 25 ~ over a salt concentration range of 10- ~ to 10 3 mol dm 3. The limiting molar eonduetivities and association constants were calculated from the expanded Fuoss-Hsia equation. The Walden product of lithium ion was not enhanced by the addition of ethyl methyl carbonate as observed in the ease of 1,2-dimethoxyethane, due to the lack of specific solvation. LiPF6 and Li(CF3SO2),N in the propylene carbonate-ethyl methyl carbonate mixed solvent formed solvent-separated ion pairs, which resulted in decreased ion association. This work is a part of our systematic study ~-6 on the transport properties of nonaqueous electrolytes. Our pre-vious study 5 on the conductometric analysis of lithium salts including LiC10~, LiBF4, LiPF6, LiAsF6, LiCF~SO3, Li(CF3SO~_)2N, and LiC~FgSO3 in propylene carbonate (PC) and ~-butyrolactone (GBL) is extended into mixtures of PC and either ethyl methyl carbonate (EMC) or 1,2-dimeth-oxyethane (DME).