Novel electrolytes for electrochemical double layer capacitors based on 1,1,1,3,3,3-hexafluoropropan-2-ol

1,1,1,3,3,3-Hexafluoropropan-2-ol (HFIP) was tested for its applicability as solvent in electrolytes for energy storage devices. A comprehensive characterization with respect to solubility, conductivity, as well as chemical and electrochemical stability was carried out with different conducting salts. Furthermore, different HFIP solutions containing standard supporting electrolytes and alkali metal fluorides, respectively, were applied in electrochemical double layer capacitor cells. Their behavior was studied with impedance spectroscopy and cyclic voltammetry at low scan rates and compared to the current benchmark electrolytes based on propylene carbonate (PC) and acetonitrile (AN). The studied electrolytes exhibit a surprisingly high potential window at glassy carbon electrodes and provide good solubility for the common conducting salts. In double layer capacitors equipped with high surface area carbon derived electrodes and small pore sizes they can easily compete with PC-based electrolytes in terms of capacitance and rate capability. Due to the presence of electrochemically active surface functionalities on the electrode material, the potential window is narrower compared to the glassy carbon electrode.