Quaternary ammonium functionalized poly(aryl ether sulfone)s as separators for supercapacitors based on activated carbon electrodes

• Quaternized poly(aryl ether sulfone) membranes were prepared as separators.
• The separators possessed excellent thermal and mechanical stabilities.
• The increasing degree of quaterization promoted performance of supercapacitors.
• The coulombic efficiency of EDLC-Q-1.1 is as high as 95% over 5000 cycles.

A series of poly(aryl ether sulfone) copolymers containing quaternary ammonium moieties were obtained by polymerization of methylated copolymers, followed by bromination and derivatization with quaternary-ammonium groups. The copolymer membranes exhibited excellent thermal stability and mechanical properties. Symmetric supercapacitor single cells based on activated carbon and quaternary ammonium functionalized poly(aryl ether sulfone) membranes were fabricated into a three-layer structure: activated carbon electrode//quaternary ammonium functionalized poly(aryl ether sulfone) separator//activated carbon electrode and characterized by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy in 6 M KOH aqueous solution. The coulombic efficiency of the supercapacitor was as high as 95% over 5000 cycles. The effect of different degree of quaternization of PAES copolymer separators on thermal and mechanical properties of separators and performance of the symmetric supercapacitor single cells were investigated.

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