New binary room-temperature molten salt electrolyte based on urea and LiTFSI

A novel room-temperature molten salt electrolyte based on urea and lithium bis(trifluoromethane sulfone)imide (LiN(SO2CF3)(2), LiTFSI) has been synthesized and characterized by differential scanning calorimetry (DSC), Raman spectroscopy, ac impedance, and cyclic voltammetry. This electrolyte appears as a liquid at room temperature, though it is composed of two solids. DSC shows that its eutectic temperature is about -37.60 degreesC. Strong interactions between the two components observed by Raman spectroscopy weaken the bonding between the anions and the cations of LiTFSI, leading to the formation of a eutectic molten salt. The conduction behavior and the electrochemical window of this electrolyte have been evaluated by ac impedance spectroscopy and cyclic voltammetry, respectively.