A series of quaternary ammonium functionalized poly(arylene ether sulfone)/poly(vinylpyrrolidone) (PAES-Q/PVP) composite membranes for separators and composite polymer electrolytes (CPEs) of electrical double-layer capacitors (EDLCs) were prepared by solution blending. EDLCs were then fabricated with the composite membranes and activated carbon electrodes. The optimized solid-state EDLC with PAES-Q/PVP composite membrane containing 40 wt% PVP entrapping 6 M KOH served as CPE exhibited a specific capacitance of 140.85 F g(-1) and an energy density of 4.81 W h kg(-1) at a current density of 0.1 A g(-1). Electrochemical cycle performance of the solid-state EDLC indicated almost 100% cycling retention and near 97% coulombic efficiency over 5000 charge-discharge cycles at 0.5 A g(-1). Additionally, the mechanical properties, thermal stability and electrochemical performance of the composite membranes with various contents of PVP were investigated as well. (C) 2016 Elsevier B.V. All rights reserved.