Enhancement of Volumetric Capacitance of Binder-Free Single-Walled Carbon Nanotube Film via Fluorination

Abstract

Robust electrode materials without the addition of binders allow increasing efficiency of electrical storage devices. We demonstrate the fabrication of binder-free electrodes from modified single-walled carbon nanotubes (SWCNTs) for electrochemical double-layer capacitors (EDLCs). Modification of SWCNTs included a sonication in 1,2-dichlorobenzene and/or fluorination with gaseous BrF3 at room temperature. The sonication caused the shortening of SWCNTs and the splitting of their bundles. As a result, the film prepared from such SWCNTs had a higher density and attached a larger amount of fluorine as compared to the film from non-sonicated SWCNTs. In EDLCs with 1M H2SO4 electrolyte, the fluorinated films were gradually defluorinated, which lead to an increase of the specific capacitance by 2.5–4 times in comparison with the initial values. Although the highest gravimetric capacitance (29 F g−1 at 100 mV s−1) was observed for the binder-free film from non-modified SWCNT, the fluorinated film from the sonicated SWCNTs had an enhanced volumetric capacitance (44 F cm−3 at 100 mV s−1). Initial SWCNT films and defluorinated films showed stable work in EDLCs during several thousand cycles.

Electrochemistry of Carbon Materials: Progress in Raman Spectroscopy, Optical Absorption Spectroscopy, and Applications

“…For these experiments, special electrochemical cells, electrolytes, electrode materials, and other parameters are important [ 141 ]. Recent works include electrochemical studies of carbon materials [ 253 , 254 , 255 , 256 , 257 , 258 , 259 , 260 , 261 , 262 , 263 , 264 , 265 , 266 , 267 , 268 , 269 , 270 , 271 , 272 , 273 , 274 , 275 , 276 , 277 , 278 , 279 , 280 , 281 ].…”

“…In Ref. [ 276 ], the electrochemical properties of pristine, sonicated, and fluorinated SWCNTs were investigated. Figure 28 shows the current density vs. potential measurements for pristine (SW), split (SW_DC), and fluorinated F-SW, and the F-SW_DC electrodes at a scan rate of 100 mV s −1 show a nearly rectangular shape.…”

“…Figure 28 shows the current density vs. potential measurements for pristine (SW), split (SW_DC), and fluorinated F-SW, and the F-SW_DC electrodes at a scan rate of 100 mV s −1 show a nearly rectangular shape. Figure 28 also shows the capacitance retention vs. cycle number measurements [ 276 ].…”

“…Licensee MDPI, Basel, Switzerland. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license [ 276 ].…”

Supercapacitor Electrodes of Blended Carbon Nanotubes with Diverse Conductive Porous Structures Enabling High Charge/Discharge Rates

“…These characteristic electrical conductions of CNTs are much superior to other carbonaceous materials such as activated carbons and templated porous carbons, which show modest conductivities due to low crystallinity (disordered, undefined chemical structures). CNTs have been reported as binder-free supercapacitor electrodes, highlighting the advantage in terms of processing electrode materials into films. − The dispersion, compressing, and templating approaches for CNT films presented the moderate control of porous structures. − During recent years, a wide variety of commercialized CNTs has become available, which are classified into three general groups of (1) low crystallinity and low SSA (large-diameter multi-walled CNTs), (2) low crystallinity and high SSA (large-diameter single- and double-walled CNTs), and (3) high crystallinity and moderate SSA (small-diameter single-walled CNTs) . Among the CNTs, single-walled CNTs in group (2), synthesized using the super growth (SG) method, possessed the highest SSA leading to higher energy density (capacitance) than other CNTs. − ,− On the other hand, the highly crystalline eDIPS and TUBALL CNTs in group (3) exhibited high electrical conductivity, suggesting high power density (charge/discharge rates).…”