Low Temperature Supercapacitor with Electrolyte Based on Hydrogen Fluoride and Ionic Liquid

The behavior of a symmetric supercapacitor with electrodes of activated carbon cloth in the electrolyte based on a solution of ionic liquid (C8H15N2PF6) in anhydrous HF is studied by cyclic voltammetry and impedancemetry in the temperature interval from -65 to +25 degrees C. The measurements are carried out in a hermetically sealed cell of perfluorinated polymer. It is shown that the capacitance of this capacitor substantially exceeds that of capacitors with conventional organic solvents. As the temperature decreases, the capacitance decreases insignificantly and the working voltage window widely extends. The increase in the internal resistance of the cell at low temperature is determined mainly by the contribution of the specific adsorption of solvated F--ions.