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

Abstract

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.

Full recycling of spent lithium ion batteries with production of core-shell nanowires//exfoliated graphite asymmetric supercapacitor

“…5b) confirm the capacity trend value obtained from the CV and plateaus were observed in same potential values. Remarkably, capacitances obtained by CV and GC are comparable to the best values reported for graphene-based supercapacitors [65][66][67]. In addition, a comparison between Rec-GPH and new battery grade graphite (TIMREX KS6) was performed.…”

High‐performance symmetric supercapacitor based on molybdenum disulfide/poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) composite electrodes deposited by spray‐coating

“…The supercapacitors were also characterized in terms of energy density ( E ) and specific power density ( P ), which are the fundamental figures of merit for any energy storage device. The energy and power densities were calculated from the GCD curves according to 80 : where C is the specific capacitance (F g −1 ), V is the applied potential, and t is the discharge time. Equations ) and () allow the obtention of E and P in Wh kg −1 and W kg −1 , respectively.…”

“…This parameter is fundamental to evaluate the charge/discharge rate characteristics of a supercapacitor 51 . Among other approaches, complex power ( S ) analysis is an interesting method to determine the time constant of supercapacitors, since it also allows to evaluate the power dissipation at a frequency range 55,80,92 . The complex power S ( ω ), as a function of angular frequency ω , is given by 51 : where the real part P ( ω ) is known as active power and the imaginary part Q ( ω ) is called reactive power.…”

“…30 The supercapacitors were also characterized in terms of energy density (E) and specific power density (P), which are the fundamental figures of merit for any energy storage device. The energy and power densities were calculated from the GCD curves according to 80 :…”

“…51 Among other approaches, complex power (S) analysis is an interesting method to determine the time constant of supercapacitors, since it also allows to evaluate the power dissipation at a frequency range. 55,80,92 The complex power S(ω), as a function of angular frequency ω, is given by 51 :…”