Conductivity of lithium bis(trifluoromethane)sulfonamide (LiTFSI)

Abstract

Thermal properties and conductivity of the lithium bis(trifluoromethane)sulfonamide (LiTSFI) were studied in a temperature range of 60–270 °C by differential scanning calorimetry (DSC) and impedance spectroscopy methods. As shown by DSC technique, at the first heating, three endothermic effects associated with dehydration, phase transition, and melting were observed On subsequent cooling and heating, only the thermal effect due to the ionic salt melting was observed. These data were confirmed by conductivity measurements. On cooling the LiTSFI sample from the molten state an abrupt decrease in the conductivity due to crystallization into the high-temperature γ-phase was observed. Thus, according to the DSC and conductivity data, the high-temperature γ-phase may be easily quenched down to room temperature. The parameters of Arrhenius dependence of conductivity for γ-phase were estimated. It was shown that this phase has rather low ionic conductivity, below 10-6 S/cm near the melting point and cannot be regarded as orientationally disordered phase.