A novel electrolyte used in high working voltage application for electrical double-layer capacitor using spiro-(1,1′)-bipyrrolidinium tetrafluoroborate in mixtures solvents

Abstract

This paper is addressed on studying the electrolytes for electrical double layer capacitors with relatively high ionic conductivity and electrochemical stability for high energy density application. A systematic analysis of the electrochemical characteristics has been presented using spiro-(1,1′)-bipyrrolidinium tetrafluoroborate (SBP-BF4) with 1.5molL−1 (M) in variety of solvent compositions including propylene carbonate (PC), ethylene carbonate (EC) and dimethyl carbonate (DMC), while the solvent mixtures are PC+DMC (1:1 in volume) and PC+DMC+EC (1:1:1 in volume). The physical properties and electrochemical performance of SBP-BF4-based electrolytes are improved by tuning solvent mixtures compositions for high working voltage application. The binary solvent system of PC+DMC electrolyte exhibits lowest viscosity of about 3.14 mPas, while the ternary solvent system of PC+DMC+EC electrolyte exhibits highest conductivity of about 18.08mScm−1. The SBP-BF4/PC-based electrolytes display excellent upper voltage hold capability about 3.5V. The binary solvent system exhibits superior rate performance, when the charge cut-off voltage is lower than 3.2V. The ternary solvent system exhibits superior rate performance than that of other two solvent systems electrolytes, when the charge cut-off voltage is higher than 3.2V. The maximum energy density and power density of EDLCs using the ternary solvent system electrolyte are 41.5Whkg−1 and 17.0kWkg−1, respectively. The spiral cylindrical capacitors based on ternary solvent system electrolyte exhibits better cycle performance than that of other two solvent system electrolytes at the high working voltages.