Novel doubly charged cation based electrolytes for non-aqueous supercapacitors

The electrochemical characteristics for the electrical double layer capacitors based on the titanium carbide derived carbon (CDC-TiC) electrodes in 0.4 M N,N-dimethyl-1,4-diazabicyclo[2,2,2]octanediium tetrafluoroborate (DMDABCO(BF4)2), 0.2 M DMDABCO(BF4)2 + 0.2 M triethylmethylammonium tetrafluoroborate (TEMABF4), and 0.4 M TEMABF4 in γ-butyrolactone (γ-BL) have been studied using cyclic voltammetry, constant current charging/discharging and electrochemical impedance spectroscopy. The ideal electrical double layer capacitor behaviour was observed in a wide region of cell voltages (U ⩽ 3.0 V) for the CDC-TiC electrodes in 0.4 M DMDABCO(BF4)2 in γ-BL. The geometry of solvation shells around DMDABCO2+, TEMA+, and BF4- have been optimized with molecular dynamics calculations and the coordination numbers equal to 15, 7 or 8, respectively, have been proposed and compared with electrochemical and gas sorption data for CDC-TiC. The gravimetric capacitance (129 F g−1), high gravimetric energy (40.6 Wh kg−1) and power (93 kW kg−1) were established for the CDC-TiC electrodes in 0.4 M DMDABCO(BF4)2 γ-BL solution.