Capacitive performance of carbon-based supercapacitors using sulfonated poly(ether ether ketone) membranes as separators: influences of casting solvents

Abstract

Sulfonated poly(ether ether ketone) (SPEEK) membranes are prepared by various casting solvents. They are adopted as separators for carbon-based electrical double-layer capacitors (EDLCs). The cyclic voltammetric curves, galvanostatic charge/discharge curves, electrochemical impedance spectroscopy and cycling performance of EDLCs are evaluated. It is found that the residual solvents in SPEEK membranes have important effects on the performances of EDLCs with SPEEK membranes due to the different interactions between residual solvents and -SO3H groups of SPEEK. After SPEEK membranes are treated in 60 °C water, the EDLC with an optimum SPEEK membrane shows a specific capacitance of 37.5 F g−1 at a current density of 1 A g−1, higher than that (30 F g−1 @ 1 A g−1) of the EDLC with a porous polypropylene membrane. Furthermore, the EDLC reveals an excellent cycling stability with capacitance retention of ∼100% after 5000 cycles at a current density of 1 A g−1. These results suggest that SPEEK membranes prepared by suitable casting solvent and activation processing can serve as a class of promising compact separators for EDLCs.