Won-Je Cho

Highly Flexible and Planar Supercapacitors Using Graphite Flakes/Polypyrrole in Polymer Lapping Film.

Flexible supercapacitor electrodes have been fabricated by simple fabrication technique using graphite nanoflakes on polymer lapping films as flexible substrate. An additional thin layer of conducting polymer polypyrrole over the electrode improved the surface conductivity and exhibited excellent electrochemical performances. Such capacitor films showed better energy density and power density with a maximum capacitance value of 37 mF cm(-2) in a half cell configuration using 1 M H2SO4 electrolyte, 23 mF cm(-2) in full cell, and 6 mF cm(-2) as planar cell configuration using poly(vinyl alcohol) (PVA)/phosphoric acid (H3PO4) solid state electrolyte. Moreover, the graphite nanoflakes/polypyrrole over polymer lapping film demonstrated good flexibility and cyclic stability.

Electrochemical supercapacitor behaviour of functionalized candle flame carbon soot

The electrochemical supercapacitor behaviour of bare, washed and nitric acid functionalized candle flame carbon soots were reported. Crystallinity and the morphology of the candle soots were recorded using X-ray diffraction analysis, scanning and transmission electron microscopy, respectively. The nitric acid functionalized candle soot showed an improved Brunauer–Emmett–Teller surface area of 137.93 from 87.495 m2 g−1 of washed candle soot. The presence of various functional groups in candle soots and the development of oxygen functionalities in the functionalized candle soot were examined through Fourier transform infrared spectroscopy and energy-dispersive X-ray analysis. Raman spectra showed the characteristic peaks corresponding to the D (diamond) and G (graphite) phase of carbon present in the candle soots. The electrochemical characterization was performed by cyclic voltammetry, galvanostatic charge/discharge test and impedance spectroscopy in 1 M H2SO4 electrolyte. The functionalized candle soot electrode showed an enhanced specific capacitance value of 187 F g−1 at 0.15 A g−1 discharge current density, which is much higher than that of bare and washed candle soot electrodes.

Supercapacitive Properties of Carbon Electrode in an Electrolyte Containing a Newly Synthesized Two-Cation Salt

To examine the effects of a two-cation ionic liquid as an electrolyte component of a supercapacitor, 1,4-bis(3-methylimidazolium-1-yl)butane tetrafluoroborate (MIBBF4), dissolved in propylene carbonate (PC) or acetonitrile (ACN), is newly synthesized and tested here for potential use as an electrolyte of capacitor. The MIBBF4 salt exhibits higher ionic conductivity in ACN than in PC. The supercapacitive properties of capacitors containing an activated carbon electrode and various electrolytes are evaluated using cyclic voltammetry and electrochemical impedance spectroscopy. The capacitor adopting the MIBBF4/ACN electrolyte shows the largest specific capacitance at low scan rates, whereas the capacitor adopting the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4)/ACN electrolyte shows the largest specific capacitance at high scan rates.