Cellulose and poly(vinyl alcohol) composite gels as separators for quasi-solid-state electric double layer capacitors

Cellulose/poly(vinyl alcohol) (PVA) composite gels are prepared as separators for quasi-solid-state electrical double-layer capacitors (EDLCs) by a simple freeze-thawing method. Fourier-transform infrared spectroscopy, scanning electron microscopy and mechanical testing machine are used to characterize the structure and morphology. Compared with the PVA gel, the as-prepared composite gels show improved network structure and enhanced mechanical properties. The cyclic voltammetric curves, galvanostatic charge/discharge curves, electrochemical impedance spectroscopy and cycling performance of EDLCs with these composite gels are also evaluated. It is found that the EDLC with the optimum composite gel can work in a voltage window of 0-1.8V and display a specific capacitance of 125.1Fg(-1) (based on active carbon on one electrode) at a current density of 1Ag(-1). Furthermore, it also has an excellent cycling stability with capacitance retention of similar to 88% after 1500 cycles. These results suggest that the composite gels can serve as a class of promising separators for EDLCs. [GRAPHICS] .