Use of organic esters as co-solvents for electrical double layer capacitors with low temperature performance

The electrochemical characteristics of the electrical double layer capacitor (EDLC) single cell based on the nanoporous carbon electrode in 1 M (C2H5)3CH3NBF4 (TEMA) solution in various non-aqueous organic carbonate and organic ester binary, ternary and quaternary solvent systems (ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl formate (MF), methyl acetate (MA) and ethyl acetate (EA)) mixed in the x:y, x:y:z and x:y:z:f volume ratios, respectively) have been studied using the cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS) methods. The specific capacitance, phase angle, series and parallel resistance values dependent on the solvent system used have been calculated. The region of ideal polarisability of nanoporous carbon electrodes ΔE ⩾ 3.0 V for 1 M TEMA in various binary, ternary and quaternary non-aqueous solvent systems has been achieved. Specific conductivity values for 1 M TEMA solution in various organic carbonate – organic ester based electrolytes have been obtained at −40 °C < T < 50 °C and compared with electrochemistry data.