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Supercapacitor (SC) cells based on microporous titanium carbide-derived carbon [C(TiC)] electrodes in room temperature ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate) have been tested by cyclic voltammetry, constant current charge/discharge, and electrochemical impedance methods at temperatures from 25 to 80°C . The limits of ideal polarizability, low frequency limiting capacitance and series resistance, time constant, complex power components, time stability, and other characteristics have been calculated and discussed. The influence of temperature on the cell capacitance, characteristic time constant values, and region of ideal polarizability has been analyzed. The comparatively high energy (40Whkg−1) and power (130kWkg−1) densities per active C(TiC) weight have been calculated, weakly depending on temperature, if T≤59°C . A comparison of the results to the corresponding data for the C(TiC)∣1M(normalC2normalH5)3CH3NBF4+acetonitrile system indicates that 1-ethyl-3-methylimidazolium tetrafluoroborate∣carbide -derived carbon SC cells demonstrate lower power densities, a narrower region of ideal polarizability, and a lower constant current cyclability at higher charge/discharge rates.

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Various ionic liquids based on 1-ethyl-3-methylimidazolium cation and tetrafluoroborate, tetracyanoborate, tris(pentafluoroethyl) trisfluorophosphate, bis(trifluoromethylsulfonyl)imide, bis(fluorosulfonyl)imide, and thiocyanate anions have been studied as electrolytes in two electrode supercapacitor test cells based on carbon cloth electrodes. Three electrode test cells were also completed and studied to analyze the processes taking place on electrode|electrolyte interface at different electrode potentials. Electrical double layer formation and adsorption kinetics of ions onto electrode surface and mass-transfer processes in porous electrode and separator matrix, dependent on the conductivity, viscosity and melting temperature of ionic liquids, have been analyzed using impedance and cyclic voltammetry data. Electrical charge delocalization has been calculated and discussed to point out and explain differences in the behavior of ionic liquids as supercapacitor electrolyte at different electrode potentials. Suitability of 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium tetracyanoborate ionic liquids as electrolytes for supercapacitors has been demonstrated.