Electrochemical Properties of LiAsF6 Solutions in Propylene Carbonate-Acetonitrile Binary Mixtures

摘要

Conductivity of LiAsF6 solutions in propylene carbonate-acetonitrile binary mixtures containing 0.2 to 1.4 mol/kg of ionophore is measured at temperatures of 283.15, 293.15, 303.15, and 313.15 K throughout the mixed solvent entire composition range. Concentration dependences of the system's conductivity can be described by the Casteel-Amis equation, except the lithium hexafluoroarsenate solution in acetonitrile. The activation energy of the charge transfer process in the studied solutions is determined; the LiAsF6 solution in acetonitrile has the lowest activation energy. From conductometry measurements in dilute solutions, the electrolyte limiting molar conductivity is calculated using the Lee-Wheaton equation. The LiAsF6 ionic association in the propylene carbonate-acetonitrile mixtures with the acetonitrile mole fraction from 0.2093 to 0.9006 is not observed; the salt is fully dissociated over this concentration range. The electrochemical stability range for 0.5 mol/kg LiAsF6 in the propylene carbonate-acetonitrile mixture was determined by means of voltammetry at 298.15 K. The decomposition potentials in the cathodic region are due to lithium electro-deposition; they depend on ionmolecule and intermolecular interactions in the system; the anodic decomposition potentials are associated with the solvent oxidation.