Electrophilic Fluorination of Graphitic Carbon for Enhancement in Electric Double‐Layer Capacitance

Abstract

Graphitic carbon is the ultimate source of carbon electrodes for practical application in energy storage devices as it is commercially available at a much lower cost in contrast to other forms of nanostructured carbon. Recently, fluorinated carbon with improved electrical conductivity and wettability has been found to possess better and efficient electrochemical storage properties. However, the development of a simple fluorination process is still a challenge. Herein, Selectfluor (F‐TEDA) is explored as a fluorinating agent for Vulcan carbon. Fluorination of carbon material results in the formation of semi‐ionic C—F (F = 8.02 at%) and ionic C—F (F = 2.71 at%) bonds as observed in X‐ray photoelectron spectroscopy analysis along with an increase in defect density (ID/IG) by 33.4%. Symmetric two‐electrode supercapacitor cells are assembled in Swagelok‐type geometry, and the specific capacitance of fluorinated carbon is found to increase by ≈15 times in contrast to pristine carbon due to induced surface polarization despite the decrease in specific surface area by ≈34%, which is remarkable. The fabricated device is stable with ≈96% capacitance retention over 10 000 cycles, resulting in enhanced supercapacitive performance.

Carbon electrodes with ionophobic characteristics in organic electrolyte for high-performance electric double-layer capacitors

“…These shifts are associated with the weakening of the C-C bond due to the redistribution of the electron density in the carbon structure resulting from the interaction between the carbon matrix and F atoms. New peaks emerge in the energy range from 287 to 291 eV because of the participation of photoelectrons emitted from C atoms in polar C-F bonding [20,21].…”

“…The excellent cycling stability of YP-F60s can be ascribed to its ionophobicity, which inhibits electrolyte degradation. The introduction of F atoms also increases repulsive interactions on the carbon lattice so that the F atoms are more stable at the edges of the lattice than in the interior region of the material [20]. This propensity renders the edge position of the carbon lattice in YP-F60s more durable and resistant to carbon corrosion during charging/discharging.…”

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

“…To improve the potential application of carbon materials as electrodes in energy storage devices, covalent functionalization (O, halogens, and amines) [ 9 ] and heteroatom (N, S, P, and B) doping are widely used [ 16 , 17 ]. The strong electronegativity and the capability of fluorine (F) to form covalent bonds with carbon atoms induce surface polarity that creates more sites for electrolyte ion adsorption, promote ion transportation, and enhance surface wettability [ 18 , 19 ]. For example, Lee et al demonstrated that the presence of fluorine in the structure of SWCNTs led to their efficient dispersion in water, while the specific capacitance of heat-treated F-SWCNTs increased due to the appearance of micropores [ 20 ].…”

Ni Ink-Catalyzed Conversion of a Waste Polystyrene–Sugar Composite to Graphitic Carbon for Electric Double-Layer Supercapacitors

“…Therefore, recycling is not a viable option, but polystyrene can be converted into a high-value, conducting carbon material for multiple applications, which is more feasible, attractive, and commercially sustainable. Carbon materials are the best choice as an electrode material because of their high conductivity, surface area, and chemical stability. , Carbon obtained from polystyrene has been utilized as an electrode material for applications in energy storage devices, surface adsorption for the removal of pollutants from water, and other catalytic applications. − For example, Fonseca et al. derived disordered carbon from waste polystyrene for applications in sodium-ion batteries .…”

“…The presence of mesoporous insulating templates such as silica, alumina, sand, MgO, and so forth affects the overall resistance of the carbon powder. ,− The processing steps involved in template removal and KOH activation deteriorate the conductivity and crystallinity of carbon despite its high specific surface area (SSA). Specifically, in electric double-layer capacitors (EDLCs), crucial factors that determine the electrochemical performance and efficiency are the accessibility of the ions to the electrode surface, conductivity, pore size distribution, wettability, thermal stability, and chemical stability of the electrode material. ,,− Even though the high surface area and porous structures facilitate the increased accessibility of electrolyte ions, the quality in terms of graphitic content and crystallinity is equally important for reducing the internal resistance of the electrode. Graphitic carbon with an optimum surface area and conductivity usually results in excellent capacitive performance with high energy and power density and long duration of life cycles. , Because of all these associated challenges, polystyrene-derived carbon has been seldomly reported in the literature for high-performance electric double-layer supercapacitors.…”