Synthesis of Free-Standing Flexible rGO/MWCNT Films for Symmetric Supercapacitor Application

摘要

Herein, we report a novel, simple, and cost-effective way to synthesize flexible and conductive rGO and rGO/MWCNT freestanding films. The effects of MWCNT addition on the electrochemical performance of rGO/MWCNT nanocomposite films are investigated in some strong base aqueous electrolytes, such as KOH, LiOH, and NaOH via three-electrode system. The supercapacitor behavior of the films is probed via cyclic voltammetry, galvanostatic charging-discharging, and electrochemical impedance spectroscopy. The structural and morphological studies of the films are performed by X-ray diffractometer, Raman spectrometer, surface area analyzer, thermogravimetric analysis, field emission scanning electron microscope and transmission electron microscope. The rGO/MWCNT film synthesized with 10?wt% MWCNTs (GP10C) exhibits high specific capacitance of 200?Fg_(?1), excellent cyclic stability with 92% retention after 15,000 long cycle test, small relaxation time constant (~?194?ms), and high diffusion coefficient (7.8457?×?10_(?9)?cm_(2)?s_(?1)) in 2?M KOH electrolyte. Furthermore, the symmetric supercapacitor coin cell with GP10C as both anode and cathode using 2?M KOH as electrolyte demonstrates high energy density of 29.4?Whkg_(?1)and power density of 439?Wkg_(?1)at current density 0.1?Ag_(?1)and good cyclic stability with 85% retention of the initial capacitance at 0.3?Ag_(?1)after 10,000?cycles. Such a high performance of the GP10C film in the supercapacitor can be ascribed to the large surface area and small hydration sphere radius and high ionic conductivity of K_(+)cations in KOH electrolyte.