A new conducting salt for high voltage propylene carbonate-based electrochemical double layer capacitors

In this paper we report about the use of N-butyl-N-methylpyrrolidinium tetrafluoroborate (PYR14BF4) as a new conducting salt for propylene carbonate (PC)-based electrochemical double layer capacitors. The electrolyte 2.3 M PYR14BF4 in PC displays conductivity and viscosity values comparable with those of conventional PC-based electrolytes and allows the realization of EDLCs with an operative voltage of 3.2 V. These high voltage EDLCs display higher energy and power compared to conventional EDLCs. Moreover, thanks to the electrochemical stability of the electrolyte, these EDLCs display high cycling stability at 3.2 V as confirmed by charge-discharge experiments as well as float voltage tests.