An Organic Electrolyte Mixed with a Quaternary Phosphonium Salt for Lithium Secondary Batteries

Abstract

The electrolytic properties of a mixed electrolyte containing methyltributylphosphonium bis(trifluoromethylsulfonyl)imide and an organic electrolyte based on lithium hexafluorophosphate, ethylene carbonate and ethyl methyl carbonate are reported. It was found that the conductivity and viscosity of the mixed phosphonium electrolyte were similar to those of the corresponding ammonium electrolyte; however, larger voltammetric response of lithium in the mixed phosphonium electrolyte and higher charge-discharge performance of the cell containing the mixed phosphonium electrolyte than those of the corresponding ammonium electrolyte were observed. In addition, the mixed phosphonium electrolyte gave relatively high cycling performance to the cell, even when compared to the more conductive organic electrolyte than the mixed phosphonium electrolyte.