Electrochemical performance of electrochemical capacitors using Cu(II)-containing ionic liquid as the electrolyte

The electrochemical behaviors of Cu(II)-containing ionic liquid 1-ethyl-3-methylmidazolium tetrafluoroborate ([EMIm]BF4) were investigated in electrochemical capacitors, which used Cu(II)-containing ionic liquid as electrolyte, porous carbon as electrode materials. The cyclic voltammetry and constant current charge–discharge results indicated that a diffusion-controlling, reversible redox reaction of Cu(II) happened in the porous carbon. A lot of dendrites deposited in porous carbon electrode analyzed by SEM and XRD should be the polymeric Cu. The occurrence of redox reaction can improve electrochemical capacitor’s capacity. The single electrode average specific capacitance can reach 225 F g−1, about 108% higher than the one used pure ionic liquid as electrolyte. The increase of average specific capacitance indicated that the faradic pseudocapacitance associated with Cu species in the redox reactions had a considerable contribution to the total capacitance of electrochemical capacitors.