Electrochemical Double Layer Capacitor Electrodes Research Articles

Investigation of Several Bio Wastes as Sustainable Carbon Materials for Supercapacitor Manufacturing

This work presents various inquests on the utilization of bio wastes, agricultural wastes and sea shells to develop activated carbon as a veritable and sustainable electrode (terminals) substance for supercapacitors-(SC) also known as electrochemical double layer capacitors (EDLC) gadgets for preserving energy. We also looked at how electrode materials are processed with a view to improve or maximise the supercapacitor performance. This review entails how several bio wastes has been singed, synthesized and utilized to produce activated carbon material for long lasting, low-cost and environmentally-friendly EDLCs via the processes of pyrolysis, carbonization, physical activation and/or chemical activation with reagents and then characterized to show attributes making them suitable for application in supercapacitor manufacturing. Some of the features making the samples suitable for use as EDLC electrode materials include pore structure, very large surface area, power density, energy density, pore volume, cyclic stability specific capacitance, iodine adsorption with other attributes. This work also showcases how the various properties were determined by different tests including Brunauer-Emmett-Teller-(BET), Fourier Transform Infrared-(FTIR) Spectrometry, Field Emission Scanning Electron Microscopy-(FESEM), Raman-Spectroscopy, Scanning Electron Microscopy-(SEM), Energy Dispersive X-Ray-(EDX), X-Ray Diffraction-(XRD), TGA-Thermo-Gravimetric Analysis, Cyclic Voltammetry-(CV), Transmission Electron Microscopy-(TEM), and other procedures.

PEMBANGUNAN PENYIMPANAN TENAGA HIJAU DARIPADA SELULOSA BAKTERIA, SELULOSA METIL DAN KANJI KENTANG

A natural polymer known as bacterial cellulose (BC), derived from a symbiotic culture of bacteria and yeast (SCOBY), is utilized as the electrodes for the electrochemical double-layer capacitors (EDLC). Bacterial cellulose which can be easily obtained from the local market, possesses an exceptional structure that allows for the elimination of non-biodegradable binders and the use of current collectors in the EDLC electrodes. A green polymer electrolyte system consisting of methylcellulose, potato starch and lithium bromide. This electrolyte demonstrates a conductivity of (1.38 ± 0.54) × 10-4 S/cm, electrochemical stability of 1.3 V, and an ionic transference number of 0.98. The optimized electrolyte is used in the EDLC. Cyclic voltammetry analysis reveals that he fabricated EDLC has a capacitive behavior without any peaks indicating redox reactions. The EDLC undergo charging and discharging for up to 5000 cycles, with specific capacitances of 26 F/g. The EDLC shows a maximum power density of 1730 W/kg, with energy density of 3.6 Wh/kg.

Graphene Nanocomposite Materials for Supercapacitor Electrodes

Graphene and related materials (graphene oxide, reduced graphene oxide) as a subclass of carbon materials and their composites have been examined in various functions as materials in supercapacitor electrodes. They have been suggested as active masses for electrodes in electrochemical double-layer capacitors, tested as conducting additives for redox-active materials showing only poor electronic conductivity, and their use as a coating of active materials for corrosion and dissolution protection has been suggested. They have also been examined as a corrosion-protection coating of metallic current collectors; paper-like materials prepared from them have been proposed as mechanical support and as a current collector of supercapacitor electrodes. This entry provides an overview with representative examples. It outlines advantages, challenges, and future directions.

Utilization of biomass wastes: coconut and Pangium edule shells as activated carbon for energy storage device material

In this research, activated carbon (AC) was synthesized from biomass wastes of coconut and Pangium edule shells and utilized as a material for electrochemical double-layer capacitors (EDLC), which are eco-friendly energy storage devices. This research was intended to bridge the need for greenhouse gas-free energy storage device and the handling of abundant biomass wastes. These efforts would undoubtedly contribute to mitigating climate change. To begin the research, the coconut and Pangium edule shells underwent carbonization at varying temperatures of 600°C and 700°C for 2 hours. Subsequently, they were subjected to chemical activation using KOH and physical activation at varying temperatures of 110°C and 600°C. Some characterization techniques, including SEM, XRD, TGA/DSC, BET, Iodine number, and proximate analysis, were employed to analyze the materials. The capacitive properties of EDLC electrodes were assessed through cyclic voltammetry (CV). After carbonization at 700°C and subsequent physical activation at 600°C, the coconut and Pangium edule shells exhibited the highest active surface area of 548.542 m2g-1 and 333.4 m2g-1, respectively. Notably, the EDLC demonstrated a maximum specific capacitance of 364.5 Fg-1 at 2 mVs-1 scan rate. These findings indicate the viability of utilizing AC from biomass waste as a promising material for EDLC applications.

Comparative Behavior of Viscose-Based Supercapacitor Electrodes Activated by KOH, H2O, and CO2.

Activated carbons derived from viscose fibers were prepared using potassium hydroxide, carbon dioxide, or water vapor as activation agents. The produced activated carbon fibers were analyzed via scanning electron microscopy and energy dispersive X-ray spectroscopy, and their porosity (specific surface area, total pore volume, and pore size distribution) was calculated employing physisorption experiments. Activated carbon fibers with a specific surface area of more than 2500 m2 g−1 were obtained by each of the three methods. Afterwards, the suitability of these materials as electrodes for electrochemical double-layer capacitors (supercapacitors) was investigated using cyclic voltammetry, galvanostatic measurements, and electrochemical impedance spectroscopy. By combining CO2 and H2O activation, activated carbon fibers of high purity and excellent electrochemical performance could be obtained. A specific capacitance per electrode of up to 180 F g−1 was found. In addition, an energy density per double-layer capacitor of 42 W h kg−1 was achieved. These results demonstrate the outstanding electrochemical properties of viscose-based activated carbon fibers for use as electrode materials in energy storage devices such as supercapacitors.

Electronically conductive MXene clay-polymer composite binders for electrochemical double-layer capacitor electrodes

Electrochemical double-layer capacitors recently attract strong attention because of their fast and stable charge/discharge characteristics and their high-power density. To improve the performance of EDLCs, it is necessary to conduct comprehensive studies on electrode, including the binder. An ideal binder for an EDLC must have high adhesion ability to the electrode components and should be electronically conductive. Here, we synthesize a composite binder consisting of MXene clay and poly(acrylonitrile-co-butyl acrylate) using an in-situ emulsion polymerization. This is a first report of an in-situ polymerization method to make a conducting composite binder with good mechanical, adhesion, and electronic conducting properties. An EDLC containing electrodes of activated carbon and MXene clay/poly(acrylonitrile-co-butyl acrylate) composite binder shows a high specific power of 8510 W kg−1 with a high specific energy of 23.6 Wh kg−1. This is a significant improvement over EDLC electrodes containing only activated-carbon and poly(acrylonitrile-co-butyl acrylate). The excellent performance is attributable to the binder's high conductivity and toughness due to improved interactions among the electrode components.

Design of Porous Carbons for Supercapacitor Applications for Different Organic Solvent-Electrolytes

The challenge of optimizing the pore size distribution of porous electrodes for different electrolytes is encountered in supercapacitors, lithium-ion capacitors and hybridized battery-supercapacitor devices. A volume-averaged continuum model of ion transport, taking into account the pore size distribution, is employed for the design of porous electrodes for electrochemical double-layer capacitors (EDLCs) in this study. After validation against experimental data, computer simulations investigate two types of porous electrodes, an activated carbon coating and an activated carbon fabric, and three electrolytes: 1.5 M TEABF4 in acetonitrile (AN), 1.5 M TEABF4 in propylene carbonate (PC), and 1 M LiPF6 in ethylene carbonate:ethyl methyl carbonate (EC:EMC) 1:1 v/v. The design exercise concluded that it is important that the porous electrode has a large specific area in terms of micropores larger than the largest desolvated ion, to achieve high specific capacity, and a good proportion of mesopores larger than the largest solvated ion to ensure fast ion transport and accessibility of the micropores.

Exfoliated graphite as electrochemical double layer capacitor electrode: Electrochemical impedance study

Official journal of the Institute of Physics - Sri Lanka. Full text articles are available. The journal also has a website at http://www.ip-sl.org/sljp/The new email for the Editor is eic.ipsl@gmail.com.

Effect of conductive polypyrrole in poly(acrylonitrile-co-butyl acrylate) water–based binder on the performance of electrochemical double-layer capacitors

Electrochemical double-layer capacitors (EDLCs) have been widely studied due to their high-power densities, despite their low energy densities compared with those of lithium ion batteries. In particular, there have been numerous studies aiming to developing high surface area carbonic material to increase EDLCs’ capacitance. However, there have been few studies examining water-based polymeric binder as an inactive component of the EDLCs’ electrodes. In this study, we introduce a conductive water-based binder which is synthesized by an in situ two-step polymerization, and use it for EDLC electrodes. Polypyrrole (PPy) is used as an electrically conducting filler for a water-based polyacrylate binder to enhance the electrochemical performance of EDLCs. Consequently, the use of the new poly(pyrrole/acrylonitrile-co-butyl acrylate) (PPyANBA) increases the specific capacitance of the EDLC electrode up to 109.7 F g−1 from the 101.0 F g−1 value of the nonconductive PANBA-containing EDLC electrode at 10,000 cycles. This is mainly attributed to the better dispersion and lower electrical resistance of the PPyANBA binder without losing the thermal, ion transport, and binding characteristics of the PANBA. Graphical abstract

Preparation and Electrochemical Properties of Porous Carbon Nanofiber Electrodes Derived from New Precursor Polymer: 6FDA-TFMB.

Porous carbon nanofibers (CNFs) with high energy storage performance were fabricated with a single precursor polymer, 6FDA-TFMB, without the use of any pore-generating materials. 6FDA-TFMB was synthesized, electrospun, and thermally treated to produce binder-free CNF electrodes for electrochemical double-layer capacitors (EDLCs). Highly porous CNFs with a surface area of 2213 m2 g−1 were prepared by steam-activation. CNFs derived from 6FDA-TFMB showed rectangular cyclic voltammograms with a specific capacitance of 292.3 F g−1 at 10 mV s−1. It was also seen that CNFs exhibit a maximum energy density of 13.1 Wh kg−1 at 0.5 A g−1 and power density of 1.7 kW kg−1 at 5 A g−1, which is significantly higher than those from the common precursor polymer, polyacrylonitrile (PAN).

Microporous Carbon Electrodes Derived from Polyacrylonitrile/Poly(Styrene-co-Acrylonitrile) Blends

Current energy demands and technological advancements will require a wide array of energy storage devices such as supercapcitors that can deliver large quantities of energy quickly. Electrochemical double layer capacitors (EDLC) are capable of cycling thousands of times with minimal drop in total capacitance, and when used with an ionic liquid electrolyte they can deliver higher energy densities due to high operating voltages. Surface area, and pore size distribution play a critical role in the performance of EDLC devices due to their relationship to capacitance. Therefore, electrospun carbon nanofibers are a promising EDLC electrode material due to their high surface area, conductivity, and cyclability. Their surface area can be tailored with the inclusion of in-situ porogens in the polymer precursor and activation during carbonization. Polymer derived carbon fibers have been produced from polyacrylonitrile (PAN) using immiscible blends with sacrificial polymers like polystyrene (PS). The resulting carbons have high surface areas (>2,000 m2g-1), but a wide distribution of pore sizes. Altering the miscibility of the sacrificial polymer with the copolymer poly(styrene-co-acrylonitrile) (SAN) affords a unique fiber morphology with a high microporosity. Figure 1

Morphological optimization and nitrogen functionalization of vertically oriented CNW for high performance electrical double layer capacitor electrode

The objective of this study is to explore the influence of topographical surface structures and nitrogen doping effects on Carbon Nano Wall (CNW) characteristics in the context of Electrochemical Double-Layer Capacitor (EDLC) electrode applications. Carbon-based materials attract significant technological and industrial interest for EDLC electrode. Among available carbon-based materials, CNW are suitable candidates for EDLC electrodes based on their extremely high surface area and open top edges, which facilitate easy electrolyte circulation. In this study, CNW are synthesized using an electron cyclotron resonance plasma-system. To evaluate the electrochemical performance of synthesized CNW with various surface morphologies, cyclic voltammetry measurements are conducted in three-electrode systems. Elemental analysis is conducted to measure the weight percentages of the synthesized CNW with varying synthesis conditions. It is found that the amount of synthesized CNW and specific capacitance saturate after 15 min of growth, but considerable differences in specific capacitance based on CNW morphology are observed. Further improvements to the specific capacitance of CNW are achieved by introducing a nitrogen plasma post-treatment without any decline in electrochemical characteristics. These encouraging results may motivate additional research on constructing suitable pore distributions for targeting high-power EDLC applications.

Surface crosslinking of 6FDA-durene nanofibers for porous carbon nanofiber electrodes in electrochemical double layer capacitors

Tailoring the chemical structures of a precursor polymer for carbon nanofibers (CNFs) produced by thermal treatment of electrospun nanofibers was studied to prepare the electrodes for electrochemical double layer capacitors (EDLCs). To improve energy storage performance of CNF electrodes, 6FDA-durene nanofibers were crosslinked by a vapor crosslinking method, and subsequently carbonized. Chemical modification via crosslinking was confirmed by FTIR spectra while the conversion of crosslinked 6FDA-durene into carbon was done by Raman spectroscopy. Electrochemical performance of these CNF electrodes was evaluated by assembling coin cells, and the CNFs derived from crosslinked 6FDA-durene nanofibers showed higher specific capacitances, energy densities and cycling stability than those from non-crosslinked ones. It was also shown that CNFs prepared using 1 min crosslinking exhibit the highest energy storage performances, a specific capacitance of 301 F g−1 (at 10 mV s−1), and the maximum energy density of 11.1 Wh kg−1 (at 0.5 A g−1) and power density of 1.8 kW kg−1 (at 6 A g−1). Surface area and porosity of CNFs, which is critical for the performance of EDLC electrodes, were studied by nitrogen adsorption/desorption measurements, and it was clearly seen that surface crosslinking of precursor polymers improved surface properties of the resultant CNFs.

Characterization Capacitive Desalinzation Cell By Using the FeIII(CN)6 3-/FeII(CN)6 4- Redox Couple As an Electrochemical Probe

Recently, a desalination technique based on porous carbon has been reported [1], merging together desalination process with electrochemical energy storage. Thanks to this new strategy, an important step forward, respect to other water desalination technologies, has been achieved. The principle is based on the capacitive adsorption of Na+ and Cl- ions in the pores of a porous activated carbon, constituting the active material of an electrochemical double layer capacitor electrode. Differently from conventional EDLC, the active material is made in the present case as slurries flowed through an electrochemical cell to achieve a continuous desalination of seat water; such system has been named Electrochemical Flow Capacitor (ELC) [2], [3]. The objective of the study is to improve the energy efficiency of the desalination process by optimizing the cell design and by selecting the proper activated carbon. To do so, we characterized a desalinization cell using different type of electrodes using the FeIII(CN)6 3-/FeII(CN)6 4- redox couple as an electrochemical probe. Our approach allowed to define a dimensionless number θ, which is proportional to the flow rate and inversely proportional to the potential scan rate, giving a guideline to sort out different operating regimes in the flow cell. Two operating regimes have been evidenced: a permanent regime for θ > 60, allowing for higher and efficient charge adsorption, and a non-permanent domain for θ < 60. Références : [1] M. E. Suss, S. Porada, X.Sun, P. M. Biesheuvel, J. Yoon and V. Presser, Energy Environ Sci., 20015, 8, 2296-2319. [2] K. B. Hatzell, E. Iwama, A. Ferris, B. Daffos, K. Urita, T. Tzedakis,F. Chauvet, P. Taberna, Y. Gogotsi, P. Simon, Electrochemistry Communications 43 (2014) 18–21. [3] Y. Gendel, A. K. E. Rommerskirchen, O. David, M. Wessling, Electrochemistry Communications 46 (2014) 152–156.

Catalytic Carbonization of Acenaphthene for the Preparation of Ordered Mesoporous Carbon CMK-1 toward Application as Electrochemical Double-layer Capacitor Electrode with Ionic Liquid Electrolyte

Ordered mesoporous carbon CMK-1 with partially graphitized domains was prepared from acenaphthene in Ni-loaded MCM-48, which showed an extremely high electric double-layer capacitance of 13.6 µF cm...

Flexible Graphene/Carbon Nanotube Electrochemical Double-Layer Capacitors with Ultrahigh Areal Performance.

The fabrication of electrochemical double-layer capacitors (EDLCs) with high areal capacitance relies on the use of elevated mass loadings of highly porous active materials. Herein, we demonstrate a high-throughput manufacturing of graphene/carbon nanotubes hybrid EDLCs. The wet-jet milling (WJM) method is exploited to exfoliate the graphite into single-few-layer graphene flakes (WJM-G) in industrial volumes (production rate ca. 0.5 kg/day). Commercial single-/double-walled carbon nanotubes (SDWCNTs) are mixed with graphene flakes in order to act as spacers between the flakes during their film formation. The WJM-G/SDWCNTs films are obtained by one-step vacuum filtration of the material dispersions, resulting in self-standing, metal- and binder-free flexible EDLC electrodes with high active material mass loadings up to around 30 mg cm-2 . The corresponding symmetric WJM-G/SDWCNTs EDLCs exhibit electrode energy densities of 539 μWh cm-2 at 1.3 mW cm-2 and operating power densities up to 532 mW cm-2 (outperforming most of the reported EDLC technologies). The EDCLs show excellent cycling stability and outstanding flexibility even in highly folded states (up to 180°).

Fabrication of carbon nanofiber electrodes using poly(acrylonitrile-co-vinylimidazole) and their energy storage performance

For electrodes in electrochemical double-layer capacitors, carbon nanofibers (CNFs) were prepared by thermal treatment of precursor polymer nanofibers, fabricated by electrospinning. Poly(acrylonitrile-co-vinylimidazole) (PAV) was employed as a precursor polymer of carbon nanofibers due to the effective cyclization of PAV polymer chains during thermal treatment compared to a typical precursor, polyacrylonitrile (PAN). PAV solutions with different comonomer compositions were prepared and electrospun to produce precursor nanofibers. Surface images obtained from scanning electron microscopy showed that their nanofibrous structure was well preserved after carbonization. It was also confirmed that electrospun PAV nanofibers were successfully converted to carbon nanofibers after the carbonization step by Raman spectroscopy. Carbon nanofiber electrodes derived from PAV showed higher specific capacitances and energy/power densities than those from PAN, which was tested by coin-type cells. It was also shown that PAV with an acrylonitrile/vinylimidazole composition of 83:17 is most promising for the carbon nanofiber precursor exhibiting a specific capacitance of 114 F/g. Their energy and power density are 70.1 Wh/kg at 1 A/g and 9.5 W/kg at 6 A/g, respectively. In addition, pouch cells were assembled to load the higher amount of electrode materials in the cells, and a box-like cyclic voltammetry was obtained with high capacitances.

Carbon additive structure influence on electrochemical double-layer capacitor electrode behavior

Electrochemical double-layer capacitors (EDLC) are widely used as power sources for peak load or peak generation leveling in transport and stationary applications sometimes in combination with accumulator battery. For such applications EDLC need low sensitivity (from lifetime and capacity point of view) to high current mode operation, which is usually crucial for traditional accumulators’ types. Capacity loss in high current mode operation due to both transport and resistive limitations is observed both for accumulators and supercapacitors but much less for latter due to initial low internal resistance and electrochemical reactions absence. Carbon nanotubes (CNT) and nanofibers (CNF) as alternative to carbon blacks as conductive additive for electrodes are good possibility to improve high current operation both for accumulators and EDLC. This paper is devoted to investigation of carbon nanotubes and nanofibers comparison with traditional carbon black additive. CNF structure usually contains more defects and has lower aspect ratio than single-walled nanotubes but this kind of materials is less expensive than CNT, that is also important for final customer. Electrode samples with Vulcan XC72R carbon black were prepared for reference measurements. All electrode samples were tested in galvanostatic charge-discharge mode at different current levels in laboratory-scale EDLC cell, characterized by impedance spectroscopy. Obtained results showed improved high-current operation for CNT-containing electrodes. Economic estimation for different kinds of additives has also been carried out.

Competition between ionic adsorption and desorption on electrochemical double layer capacitor electrodes in acetonitrile solutions at different currents and temperatures

The operation of electrochemical double layer capacitors at high currents and viscosities and at low temperatures is difficult. Under these conditions, ion transport is limited, and some of the electrode area is unavailable for adsorption, which results in a low capacitance. Increasing the temperature helps to increase the ionic movement, leading to enhanced adsorption and increased capacitance. In contrast, ion desorption (self-discharge) surpasses the capacitance improvement when ions gain a high amount of energy with increasing temperature. For example, temperatures as high as 70 °C cause a very high rate of ionic desorption in acetonitrile solutions in which the individual properties of the two electrolytes—tetraethylammonium tetrafluoroborate (TEA BF4) and ethylmethylimidazolium tetrafluoroborate (EMI BF4)—are not distinguishable. The capacitance improvement and self-discharge are balanced, resulting in a capacitance peak at mid-range temperatures, i.e., 35–45 °C, in the more viscous electrolyte, i.e., TEA BF4. The less viscous electrolyte, i.e., EMI BF4 has a wider capacitance peak from 25 to 45 °C and higher capacitance than that of TEA BF4. Because the maximum power is obtained in the mid-temperature range (35–45 °C), it is necessary to control the viscosity and temperature to obtain the maximum power in a given device.

Increase of porosity by combining semi-carbonization and KOH activation of formaldehyde resins to prepare high surface area carbons for supercapacitor applications

A series of porous carbon samples were prepared by combining a semi-carbonization process of acidic polymerized phenol-formaldehyde resins and a following chemical activation with KOH used in different ratios to increase specific surface area, micropore content and pore sizes of the carbons which is favourable for supercapacitor applications. Samples were characterized by nitrogen physisorption, powder X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The results show that the amount of KOH, combined with the semi-carbonization step had a remarkable effect on the specific surface area (up to SBET: 3595m2g−1 and SDFT: 2551m2g−1), pore volume (0.60–2.62cm3g−1) and pore sizes (up to 3.5nm). The carbons were tested as electrode materials for electrochemical double layer capacitors (EDLC) in a two electrode setup with tetraethylammonium tetrafluoroborate in acetonitrile as electrolyte. The prepared carbon material with the largest surface area, pore volume and pore sizes exhibits a high specific capacitance of 145.1Fg−1 at a current density of 1Ag−1. With a high specific energy of 31Whkg−1 at a power density of 33028Wkg−1 and a short time relaxation constant of 0.29s, the carbon showed high power capability as an EDLC electrode material.