Lithium Salt Solutions in Mixed Sulfone and Sulfone-Carbonate Solvents: A Walden Plot Analysis of the Maximally Conductive Compositions

In seeking solutions to the problem of the high viscosity of electrochemically stable sulfone electrolyte solvents for high voltage lithium cells, we have explored a number of binary sulfone + cosolvent systems, including all-sulfone cases. We report systems that at 55 °C are nearly as conductive as the “standard” carbonate-based electrolyte and may merit further study. We employ a plot based on the classical Walden rule as a primary tool for assessing the loss of potential conductivity to undesirable ion-pairing phenomena. To conclude, we briefly consider the possible alternatives to molecular solvent-based electrolytes for high voltage cathode cells.