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Showing papers on "Supercapacitor published in 2003"


Journal ArticleDOI
TL;DR: In this paper, the results obtained on the electrochemical behavior of electrochemical capacitors assembled in nonaqueous electrolyte are presented and the impedance of the supercapacitors is discussed in terms of complex capacitance and complex power.
Abstract: This paper presents the results obtained on the electrochemical behavior of electrochemical capacitors assembled in nonaqueous electrolyte. The first part is devoted to the electrochemical characterization of carbon-carbon 4 cm2 cells systems in terms of capacitance, resistance, and cyclability. The second part is focused on the electrochemical impedance spectroscopy study of the cells. Nyquist plots are presented and the impedance of the supercapacitors is discussed in terms of complex capacitance and complex power. This allows the determination of a relaxation time constant of the systems, and the real and the imaginary part of the complex power vs. the frequency plots give information on the supercapacitor cells frequency behavior. The complex impedance plots for both a supercapacitor and a tantalum dielectric capacitor cells are compared. © 2003 The Electrochemical Society. All rights reserved.

1,674 citations


Journal ArticleDOI
TL;DR: In this article, the complementary use of electrochemical capacitors (so-called supercapacitors) in hybrid electric power generation by rechargeable batteries and fuel cells was explored, where the authors proposed two types of hybrid battery/capacitor system: one based on combining an electrochemical capacitor cell with a rechargeable battery or a fuel cell in a load-leveling function, e.g. in an electric vehicle power train; and the other based on combination of a faradaic battery-type electrode coupled internally with a capacitative electrode in a two-electro
Abstract: The basis of the complementary use of electrochemical capacitors (so-called supercapacitors) in hybrid electric power generation by rechargeable batteries and fuel cells is explored. Electrochemical capacitors are of two types: one where the interfacial double-layer capacitance of high specific area carbon materials is the basis of electric charge storage (as ions and electrons); and the other where pseudocapacitance, associated with electrosorption and surface redox processes at high-area electrode materials, e.g. RuO2, or at conducting polymers, provides the basis of charge storage. The former, double-layer, type of capacitance stores charge non-faradaically while the latter type, pseudocapacitance, stores charge indirectly through faradaic chemical processes but its electrical behaviour is like that of a capacitor. Two types of hybrid battery/capacitor system are recognized: one based on combination of an electrochemical capacitor cell with a rechargeable battery or a fuel cell in a load-leveling function, e.g. in an electric vehicle power train; and the other based on combination of a faradaic battery-type electrode coupled internally with a capacitative electrode in a two-electrode hybrid module (termed an asymmetric capacitor). Optimization of operation of such systems in terms of balancing of active masses, of power and charge densities, and choice of maximum but limited states-of-discharge, is treated.

524 citations


Journal ArticleDOI
TL;DR: In this article, the specific energy, specific power, fast-charge capability, low temperature operation, cycle-life and self-discharge of five energy storage devices were compared.

517 citations


Journal ArticleDOI
TL;DR: In this article, the specific surface area of activated carbon nanofibers (ACNFs) activated at 700°C was the highest but mesopore volume fraction of that was lowest.
Abstract: Poly(acrylonitrile) solutions in dimethylformamide were electrospun to be webs consisting of 300 nm ultrafine fibers. The webs were oxidatively stabilized and activated by steam resulting in activated carbon nanofibers (ACNFs). The specific surface area of the ACNF activated at 700 °C was the highest but mesopore volume fraction of that was lowest. On the other hand, the ACNFs activated at 800 °C showed opposite trends to those activated at 700 °C. The high specific surface area, mainly due to the micropores, introduced maximum specific capacitance at low current density (173 F/g at 10 mA/g). The elevated volume fraction of mesopores gave maximum specific capacitance at high current density (120 F/g at 1000 mA/g). The behavior is explained on the basis of ion mobility in the pores.

474 citations


Proceedings ArticleDOI
12 Oct 2003
TL;DR: In this article, the authors employed the method of electrochemical impedance spectroscopy to find new equivalent-circuit models for supercapacitors and lithium-ion batteries, and used simulation-based design methods to predict performance of modern power electronic systems.
Abstract: To predict performance of modern power electronic systems, simulation-based design methods are used. This work employs the method of electrochemical impedance spectroscopy to find new equivalent-circuit models for supercapacitors and lithium-ion batteries.

399 citations


Journal ArticleDOI
TL;DR: In this article, the performance of supercapacitors with multiwalled carbon nanotubes deposited with conducting polymer as activate materials was greatly enhanced in contrast with electric double-layer super-capacitor with carbon nanotsubes due to the conducting polymer's faradaic effect.

283 citations


Journal ArticleDOI
TL;DR: In this article, the electrochemical double-layer (ECDL) capacitors have been made using various types of CNT and activated carbon (a-C) as electrode material.

282 citations


Proceedings ArticleDOI
12 Oct 2003
TL;DR: In this paper, different equalization concepts are analyzed and evaluated, and a simulation approach for the design of supercapacitor systems is proposed, where results from an automotive application are presented.
Abstract: Supercapacitors, also known as ultracapacitors or electric double-layer capacitors (ELDCs), are electrical energy storage devices, which offer high power density, extremely high cycling capability, and mechanical robustness. Due to their electrical performance, supercapacitors have a high potential to be used in industrial applications. To improve the performance, reliability, and lifetime of these capacitors, charge-balancing circuits are employed. In this paper, different equalization concepts are analyzed and evaluated. In addition, a simulation approach for the design of supercapacitor systems is proposed. As an example, results from an automotive application are presented.

279 citations


Journal ArticleDOI
TL;DR: In this article, an experimental study of the electrical and thermal behavior of supercapacitors for power electronics and transportation applications is presented, and simulation results are presented, analyzed and compared.

248 citations


Journal ArticleDOI
TL;DR: In this article, a conducting polymer matrix is integrated into a polyaniline matrix to form a hybrid material to harness the electrochemical activity of nanosized oxide clusters, which can be put to work in energy storage applications.

225 citations


Proceedings ArticleDOI
23 Jun 2003
TL;DR: In this paper, the application of a supercapacitor bank when used as a power buffer to smooth rapid power fluctuations in and out of the battery of an electric or hybrid vehicle is investigated.
Abstract: This paper investigates the application of a supercapacitor bank when used as a power buffer to smooth rapid power fluctuations in and out of the battery of an electric or hybrid vehicle. The study considers the simple case where the supercapacitor bank is connected directly in shunt with the battery as well as the case where it is connected through a DC/DC converter that is necessary to achieve optimal performance. The work is illustrated through computer simulations during vehicle acceleration and deceleration. Partial experimental data on a prototype circuit is also shown. Proper design of such a hybrid electrical energy storage system is expected to result in substantial benefits to the well being of the battery bank.

Journal ArticleDOI
TL;DR: In this article, the specific capacitance of RuO 2 /malt-walled carbon nanotube (CNT) nanocomposites has been investigated by using cyclic voltammetry at different scan rates.
Abstract: Electrochemical characteristics of electrodes for supercapacitors built from RuO 2 /maltiwalled carbon nanotube (CNT) nanocomposites have been investigated. Capacitances have been estimated by cyclic voltammetry at different scan rates from 5-50 mV/s. Electrostatic charge storage as well as pseudofaradaic reactions of RuO 2 nanoparticles have been affected by the surface functionality of CNTs due to the increased hydrophilicity. Such hydrophilicity enables easy access of the solvated ions to the electrode/electrolyte interface, which increases faradaic reaction site number of RuO 2 nanoparticles. The specific capacitance of RuO 2 /pristine CNT nanocomposites based on the combined mass was about 70 F/g (RuO 2 : 13 wt % loading). and the specific capacitance based on the mass of RuO 2 was 500 F/g. However, the specific capacitance of RuO 2 /hydrophilic CNT nanocomposites based on the combined mass was about 120 F/g (RuO 2 : 13 wt % loading), and the specific capacitance based on the mass of RuO 2 was about 900 F/g.

Patent
30 Jun 2003
TL;DR: In this article, a supercapacitor made with electrodes comprising activated carbonaceous polymer-nanotube material in contact with current collectors and permeated with an electrolyte, which may be either fluid or solid, is presented.
Abstract: The present invention relates to a supercapacitor, also known as an electrical double-layer capacitor or ultracapacitor, having electrode material comprising single-wall carbon nanotubes. The carbon nanotubes can be derivatized with functional groups. The electrode material is made by preparing a polymer-nanotube suspension comprising polymer and nanotubes, forming the polymer-nanotube suspension into a polymer-nanotube composite of the desired form, carbonizing the polymer-nanotube composite to form a carbonaceous polymer-nanotube material, and activating the material. The supercapacitor includes electrode material comprising activated carbonaceous polymer-nanotube material in contact with current collectors and permeated with an electrolyte, which may be either fluid or solid. In the case of a fluid or compressible electrolyte, an electrolyte-permeable separator or spacer is interposed between the electrodes to keep the electrodes from shorting. The supercapacitor made with electrodes comprising underivatized single-wall carbon nanotubes and polymer that has been carbonized and activated appears to operate as a non-Faradaic supercapacitor.

Journal ArticleDOI
TL;DR: In this article, the authors presented the work carried out within a European Union (EU) project which led to the development of 3 V and 1.5 kF preseries supercapacitor modules and 2 kW stacks based on hybrid cells with poly(3-methylthiophene) as positive electrode and activated carbon as the negative electrode with propylene carhonate-tetraethylammonium tetrafluoroborate electrolyte.
Abstract: This paper presents the work carried out within a European Union (EU) project which led to the development of 3 V and 1.5 kF preseries supercapacitor modules and 2 kW stacks based on hybrid cells with poly(3-methylthiophene) as positive electrode and activated carbon as the negative electrode with propylene carhonate-tetraethylammonium tetrafluoroborate electrolyte. These prototypes, which display a concept of hybrid cell operating with a high-surface-area activated carbon and a conventional electronically conducting polymer, both commercially available, and with a nontoxic and nonvolatile electrolyte, provide a successful response to the market demand for high power and energy supercapacitors operating with an environmentally friendly electrolyte.

Journal ArticleDOI
TL;DR: Nonaqueous asymmetric hybrid electrochemical supercapacitors using a nanostructured Li 4 Ti 5 O 12 anode and an activated carbon cathode were built in the same technology as plastic Li-ion batteries as mentioned in this paper.

Journal ArticleDOI
TL;DR: In this paper, the pseudocapacitive behavior of multwalled carbon nanotubes (MWNTs) functionalized with hydrous ruthenium oxide in 1 M sulfuric acid for supercapacitor applications was reported.

Journal ArticleDOI
TL;DR: In this article, composite electrodes for supercapacitors were prepared by electropolymerization of polyaniline (PANI) on the surface of activated-porous carbons and the surface morphology and the chemical composition of composite electrodes were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).

Journal ArticleDOI
TL;DR: In this article, both carbon fibre reinforced and polymeric bound aerogel electrodes based on polytetrafluoroethylene (PTFE) have been investigated with respect to their electrical conductivity, surface area and capacitive performance.
Abstract: Carbon aerogels are prepared here via pyrolysis of resorcinol-formaldehyde aerogels. Their open porous and electrically conductive structure renders carbon aerogels suitable for the application in supercapacitors. Different types of electrodes can be derived from the sol-gel-precursors of carbon aerogels: Monolithic fibre-reinforced electrodes and polymer-carbon compounds. Both carbon fibre reinforced and polymeric bound aerogel electrodes based on polytetrafluoroethylene (PTFE) have been investigated in this work with respect to their electrical conductivity, surface area and capacitive performance. The capacitance of both electrode types is above 65 F/cm3 in aqueous electrolytes and this meets the demands of supercapacitor electrodes.

Journal ArticleDOI
TL;DR: In this paper, a symmetric supercapacitor based on carbon polyacrylonitrile (PAN) covered by an electronically conducting polymer was tested for capacity, energy and power density and self-discharge.
Abstract: Polyaniline was electrochemically synthesized on carbon polyacrylonitrile aerogel electrodes for use as active material in supercapacitor devices. Electrochemical characterization was performed by cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and charge–discharge experiments in aqueous medium. Two types of electrochemical phenomenon were observed; the first is based on electrostatic energy storage in the double layer at the interface solution/carbon polyacrylonitrile (PAN) aerogel, the other is associated with the redox processes in polyaniline, for which the faradaic charge depends on the potential range. The performance of the supercapacitor was tested for capacity, energy and power density and self-discharge. Specific capacitance as high as 230 F g−1 was reached. A symmetrical supercapacitor showed good cyclability (over 3000 cycles) during repeated charge–discharge cycles. The results are very promising and demonstrate the viability of a symmetric supercapacitor based on carbon PAN aerogel covered by an electronically conducting polymer.

Journal ArticleDOI
TL;DR: In this paper, a linear charge/discharge curve can be obtained between 0 and 3 V when the weight of a conducting polymer is larger than that of the negative carbon electrode.
Abstract: Hybrid electrochemical supercapacitors based on carbon and conducting polymers as negative and positive electrodes, respectively, have been investigated. Poly-(3-fluorinatedphenyl)thiophene and poly(ethylenedioxythiophene) derivatives showing various ranges of electrochemical activity and capacitance values were evaluated as positive electrodes. It was shown that the mass and capacitance of the polymers have a significant effect on the charge/discharge characteristics and performance of such hybrid electrochemical supercapacitors. The experimental conditions that should be used to obtain specific charge/discharge curves are presented. A linear charge/discharge curve can be obtained between 0 and 3 V when the weight of conducting polymer is larger than that of the negative carbon electrode. In contrast, a battery-like charge/discharge curve is recorded when a smaller conducting polymer weight, relative to that of the carbon electrode, is used.

Journal ArticleDOI
TL;DR: In this paper, a supercapacitor was fabricated using fluorinated single-walled carbon nanotubes (SWCNTs), and the specific capacitance of the fluorinated SWCNT is smaller than that of the pristine sample particularly at large discharge current density.
Abstract: We have fabricated electrodes for a supercapacitor using fluorinated single-walled carbon nanotubes (SWCNTs). Although the specific surface areas of the pristine and fluorinated SWCNTs are similar, the electrochemical reactions are different significantly from each other. The specific capacitance of the fluorinated SWCNTs is smaller than that of the pristine sample particularly at large discharge current density, which can be attributed to the micropores formed during fluorination. After heat treatment at 900 °C for 30 min, the nonredox reaction is dominant, and furthermore, the fluorinated sample gives a larger specific capacitance than the pristine sample.

Journal ArticleDOI
TL;DR: In this article, an in depth evaluation of membrane electrode assemblies (MEAs, capacitor devices without a casing) was carried out and the highest specific capacitance, specific energy and specific power values depend on the method of cell-to-cell comparison.

Journal ArticleDOI
TL;DR: In this paper, a double layer capacitance of carbon nanotubes with H 2 SO 4 was investigated and it was shown that electrons are the majority carriers with a carrier concentration of 1.35×10 20 cm −3.

Journal ArticleDOI
TL;DR: In this article, a pseudo-two-dimensional model for the general application of supercapacitors consisting of an oxide/carbon composite electrode was developed for the purpose of optimizing cell configurations and operating conditions.
Abstract: A pseudo two-dimensional model is developed for the general application of supercapacitors consisting of an oxide/carbon composite electrode. The model takes into account the diffusion of protons in the oxide particle by employing the method of superposition. RuO 2 /carbon system is modeled as a specific example. From the simulation data, it is found that the oxide particle size and proton diffusion coefficient have an enormous effect on the performance at high discharge rate due to the limitation of proton transport into RuO 2 particles. With increasing carbon ratio, the porosity of electrode increases, which causes the potential drop in solution phase to decrease. However, excess of carbon lowers the total capacitance because the pseudocapacitance from RuO 2 decreases. Finally, the present model successfully provides a methodology to optimize cell configurations and operating conditions.

Journal ArticleDOI
TL;DR: In this paper, a new electric double layer capacitor (EDLC) was constructed by using polymer hydrogel electrolyte prepared from crosslinked potassium poly(acrylate) and KOH aqueous solution, and its electrochemical characteristics were investigated by cyclic voltammetry and charge-discharge cycle tests, compared with a case of the cell using only a KOH-Aqueous Solution as an electrolyte.

Journal ArticleDOI
TL;DR: In this article, a supercapacitor electrode was synthesized by cyclic voltammetric plating of RuO 2 onto a porous and highly conductive, Sb (6 mol %)-doped SnO 2 particulate substrate that possessed a large surface area (75 m2/g).
Abstract: A supercapacitor electrode was synthesized by cyclic voltammetric plating of RuO 2 onto a porous and highly conductive, Sb (6 mol %)-doped SnO 2 particulate substrate that possessed a large surface area (75 m2/g). A specific capacitance of 930 F/g for the Ru0 2 component in 1 M H 2 S0 4 ( aq) and an overall specific energy of ∼0.5 Wh/kg at a specific power ≥ 1.5 kW/kg were achieved by an optimized crystallization protocol (150°C). Comparative studies demonstrated that this composite electrode exhibited a far superior performance to electrodes having RuO similarly plated onto either smooth Ti or porous conductive carbon black.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the performance of the magnetite supercapacitor in aqueous electrolytes of Na2SO3, KOH and Na2O4.
Abstract: Operating characteristics, including capacitance, leakage current, operating potential range, cycling stability and open-circuit self-discharge behaviours, of the magnetite (Fe3O4) supercapacitor, containing 10 wt % carbon black as conductive additive, in aqueous electrolytes of Na2SO3, KOH and Na2SO4 were investigated. Although the capacitance of the oxide was found to depend heavily on electrolyte composition, the self-discharge mechanism in these electrolytes appeared to be the same. Reduction in the dissolved oxygen content (DOC) of the electrolyte reduced the leakage current and profoundly improved the cycling stability. In particular, Na2SO3(aq) gives the highest capacitance, nearly 30 F (g-Fe3O4)−1 or 80 μF cm−2 of actual surface area, with an operation range of 1.1 V based on a leakage current less than 0.1 mA F−1, and the electrode showed no deterioration after 104 cycles under a DOC < 0.1 ppm.

Proceedings ArticleDOI
15 Jun 2003
TL;DR: In this paper, a 1 kVA fuel cell powered line-interactive UPS system employing modular (fuel cell and power converter) blocks is introduced, and two commercially available PEMFC (25-39 V, 500 W) modules along with suitable DC/DC and DC/AC power electronic converter modules are employed.
Abstract: In this paper a 1 kVA fuel cell powered line-interactive UPS system employing modular (fuel cell and power converter) blocks is introduced. Two commercially available PEMFC (25-39 V, 500 W) modules along with suitable DC/DC and DC/AC power electronic converter modules are employed. A supercapacitor module is also employed to compensate for the instantaneous power fluctuations and overcome the slow dynamics of the fuel processor such as reformers. Further energy stored in the supercapacitor is also utilized to handle a momentary overload such as 200% for a short duration. Due to the absence of batteries, the system satisfies the demand for an environmentally friendly clean source of energy. A complete design example illustrating the amount of hydrogen storage required for 1 hr power outage, and sizing of supercapacitors for transient load demand is presented for a 1 kVA UPS. Simulation and experimental results show the validity and feasibility of the 1 kVA fuel cell power plant.

Journal ArticleDOI
TL;DR: Li et al. as discussed by the authors investigated an all solid-state thin-film microsupercapacitor (TFSC) fabricated with tungsten cosputtered ruthenium oxide electrodes (W-RuO2) and LiPON electrolyte.
Abstract: We investigate an all solid-state thin-film microsupercapacitor (TFSC) fabricated with tungsten cosputtered ruthenium oxide electrodes (W-RuO2) and LiPON electrolyte. It is shown that the room-temperature charge–discharge behavior of the TFSC is similar to that of a bulk-type supercapacitor. It is also shown that the W-RuO2-based TFSC exhibits a higher discharge specific capacitance and more stable cyclibility, compared with those of the RuO2-based TFSC. Based on the pseudocapacitance of the oxide electrodes, the cycling behavior of the TFSCs and tungsten cosputtering effect on the electrochemical properties of TFSCs are described.

Patent
20 May 2003
TL;DR: In this article, a bipolar roll is used for the assembly of supercapacitor modules, which can be connected in series, in parallel or in a combination of the two connections to fabricate integrated super-capacitors with high energy density.
Abstract: The energy content of supercapacitor is determined by its capacitance value and working voltage. To attain a high capacitance and a high voltage, several pieces of electrodes and separators are spirally wound with edge sealing to form a bipolar supercapacitor in cylindrical, oval or square configuration. While the winding operation effectively provides a large surface area for high capacitance, the bipolar packaging instantly imparts a unitary roll a minimum working voltage of 5V on using an organic electrolyte. The bipolar roll is a powerful building block for facilitating the assembly of supercapacitor modules. Using containers with multiple compartments, as many bipolar rolls can be connected in series, in parallel or in a combination of the two connections to fabricate integrated supercapacitors with high energy density as required by applications.