Effect of viscosity and volume on the specific conductivity of lithium salts in solvent mixtures

As part of a study on the optimization of the electrolyte for high energy lithium batteries, the conductivity, viscosity and density of LiAsF6, LiBr, and LiClO4 were measured in aprotic solvent mixtures. The conductivity of lithium bis(trifluoromethylsulfone)imide (LiTFSI) was also obtained in a large number of mixed aprotic solvents. The solvents were chosen to verify the effect of various parameters such as viscosity, permittivity, volume, acceptor number and donor number on the conductivity. These results were used to develop a simple model for excess conductivities based on the viscosity and volume of the pure solvents. Without adjustable parameters, this model predicts the correct sign of the excess conductivities in approximate to 90% of the cases and the magnitude of the conductivity of the ternary mixtures within an average of 15%. Deviations from the predictions are mostly observed with solvents of low permittivity and this supports the hypothesis that a different conduction mechanism is in operation at high concentration in these solvents, and the solvating power of these solvents plays an important role in this mechanism. (C) 1999 Elsevier Science Ltd. All rights reserved.