Showing papers on "Supercapacitor published in 2002"
TL;DR: In this paper, it is shown that for these applications the electrochemical properties of multiwalled and single walled (SWNTs) nanotubes are essentially dominated by their mesoporous character, and an almost linear dependence has been found between the mesopore volume and Cirr.
1,013 citations
TL;DR: In this paper, the α-MnO2 powder was synthesized by a simple coprecipitation technique and tested as active electrode material for an electrochemical supercapacitor, showing that an average capacitance of 166 F/g can be reproducibly obtained within a voltage range −0.4/+0.5 V vs Hg/Hg2SO4 using a sweep rate of 2 mV/s.
Abstract: α-MnO2 was synthesized by a very simple coprecipitation technique and tested as active electrode material for an electrochemical supercapacitor. The powder presents a poorly crystallized cryptomelane phase with a chemical composition of K0.05MnO2H0.10·0.15H2O. Different aqueous electrolytes were tested including 0.1 M Na2SO4, 0.5 M K2HPO4/KH2PO4 buffer solution, 0.3 M H2SO4, and 1 M NaOH, but interesting pseudocapacitance behavior was only observed in the case of 0.1 M Na2SO4. Further testing using this electrolyte showed that an average capacitance of 166 F/g can be reproducibly obtained within a voltage range −0.4/+0.5 V vs Hg/Hg2SO4 using a sweep rate of 2 mV/s. This interesting value is mainly due to the chimisorption of Na+ ions and/or protons at the surface of the α-MnO2 electrode. Nearly all the Mn surface atoms are involved in the pseudocapacitive process. Therefore, the high specific capacitance seems to be related to the high surface area of the MnO2 powder rather than intercalation of Na+ ions ...
912 citations
TL;DR: In this article, polyaniline doped with HCl and LiPF6 (Pani-LiPF6) is used as the active electrode material of symmetric redox supercapacitors.
519 citations
TL;DR: In this article, a nanocomposite electrode of single-walled carbon nanotube (SWNT) and polypyrrole (Ppy) is fabricated to improve the specific capacitance of the supercapacitor.
Abstract: A nanocomposite electrode of single-walled carbon nanotube (SWNT) and polypyrrole (Ppy) is fabricated to improve the specific capacitance of the supercapacitor. The individual nanotubes and nanoparticles are uniformly coated with Ppy by in situ chemical polymerization of pyrrole. To characterize the SWNT-Ppy nanocomposite electrodes, a charge-discharge cycling test for measuring specific capacitance, cyclic voltammetry, and an ac impedance test are executed. The SWNT-Ppy nanocomposite electrode shows much higher specific capacitance than pure Ppy and as-grown SWNT electrodes, due to the uniformly coated Ppy on the SWNTs. The effects of the conducting agent added in the nanocomposite electrodes on specific capacitance and internal resistance of supercapacitors are also investigated. © 2002 The Electrochemical Society. All rights reserved.
420 citations
TL;DR: In this paper, a novel class of electrochemical supercapacitor electrode material has been electrochemically synthesized from a manganese halide complex in water-containing acetonitrile electrolyte at room temperature.
408 citations
TL;DR: In this article, the performance data of conventional and especially designed thiophene-based conducting polymers for use as positive and negative electrodes in n/p type supercapacitors is summarized.
350 citations
TL;DR: In this paper, commercial supercapacitors from Saft, Maxwell, Panasonic, CCR, Ness, EPCOS, and Power Systems were tested under constant current and constant power discharges to assess their applicability for power-assist applications in hybrid electric vehicles (HEVs).
339 citations
TL;DR: In this article, nanocrystalline manganese oxides have been synthesized by reducing aqueous KMnO 4 solution with various reducing agents such as potassium borohydride, sodium dithionite, sodium hypophosphite, and hydrochloric acid under various controlled pH conditions.
Abstract: With an objective to develop inexpensive electrode materials for electrochemical redox capacitors, nanocrystalline manganese oxides have been synthesized by reducing aqueous KMnO 4 solution with various reducing agents such as potassium borohydride, sodium dithionite, sodium hypophosphite, and hydrochloric acid under various controlled pH conditions. The products have been characterized by X-ray diffraction, thermogravimetric analysis, surface area measurements, and cyclic voltametry in various neutral electrolytes such as aqueous NaCI, KCl, LiCI, and Na 2 SO 4 . Optimized samples exhibit specific capacitance values of around 250 F/g in the range of 0-1 V vs. SCE with excellent cyclability in 2 M NaCI electrolyte.
313 citations
TL;DR: Amorphous nanostructured composite materials with different RuO 2 loadings on carbon were prepared by colloidal method as mentioned in this paper, which was found to be critical in optimizing the electrochemical performance of this material.
286 citations
Patent•
06 Apr 2002TL;DR: In this article, a novel process for the preparation of carbon-based structured materials with controlled topology, morphology and functionality is presented, where the nanostructured materials are prepared by controlled carbonization, or pyrolysis, of precursors comprising phase separated copolymers.
Abstract: The present invention comprises a novel process for the preparation of carbon based structured materials with controlled topology, morphology and functionality. The nanostructured materials are prepared by controlled carbonization, or pyrolysis, of precursors comprising phase separated copolymers. The carbon based structures can find application in photovoltaics, supercapacitors, batteries, fuel cells, computer memory, carbon electrodes, carbon foams, actuators and hydrogen storage.
231 citations
TL;DR: In this paper, composite electrodes for supercapacitors are prepared via chemical polymerization of pyrrole (Py) on the surface of a porous graphite fiber matrix, and capacitance properties are investigated with cyclic voltammetry (CV), ac impedance spectroscopy and charge-discharge tests.
TL;DR: In this article, the authors show that the distribution of R and C elements in a porous electrode structure leads to a decline of energy-density with operating power-density as current drain is increased.
Patent•
20 Mar 2002
TL;DR: In this article, a mesostructural electroactive material comprising nanoparticles forming a three-dimensional framework structure of mesoporous texture having a bicontinuous junction of large specific surface area with the electrolyte is described.
Abstract: A high kinetics rate electrochemical cell in which at least one of the electrodes is composed of a mesostructural electroactive material comprising nanoparticles forming a three-dimensional framework structure of mesoporous texture having a bicontinuous junction of large specific surface area with the electrolyte. A low temperature method of preparation of the electrodes employs a high-speed deposition of the electrically active material in the form of a thin film. The application of said electrodes in high power lithium ion insertion batteries, photovoltaic cells, supercapacitors and fast electrochromic devices is disclosed.
TL;DR: In this article, the performance of a polyaniline-activated carbon, hybrid electrochemical capacitor was evaluated by using a constant charge-discharge test, and a specific capacitance of 380 F g−1 was obtained.
TL;DR: In this paper, a supercapacitor comprising a poly(3,4-ethylendioxythiophene) (PEDOT) and poly (3, 4-propylenedioxyntiophene (PProDOT) was used as electrode couples for the capacitor and a pair of gel electrolyte layers disposed between the electrodes.
Abstract: A supercapacitor comprising a poly(3,4-ethylendioxythiophene) (PEDOT) and poly(3,4-propylenedioxythiophene) (PProDOT) as electrode couples for the capacitor and a pair of gel electrolyte layers disposed between the electrodes. The gel electrolytes are separated by a battery paper and are selected from a group consisting of a lithium salt and an organic electrolyte.
TL;DR: In this paper, the integration of thin monolithic aerogel composites in button cell casings is presented, where carbon fibers are incorporated into the aerogels skeleton to increase the external electrode area in the button cells.
TL;DR: In this article, a polyaniline (PANI) coated supercapacitor was applied to stainless-steel (SS) electrodes to obtain a capacitance of about 450 F over a long cycle-life.
07 Nov 2002
TL;DR: In this paper, a multiple input DC-DC power converter devoted to combine the power flow of multi-source on-board energy systems is presented. But the authors focus on the optimization of the output capacitors bank in relation to the RMS value of the current ripple is investigated.
Abstract: Customer demands for greater acceleration, performance, and vehicle range in pure EVs plus mandated requirements to further reduce emissions in HEVs increase the appeal for combined on-board energy storage systems and generators. This paper deals with a multiple input DC-DC power converter devoted to combine the power flow of multi-source on-board energy systems. The proposed energy storage arrangement includes fuel cell generator, ultracapacitor tank, and battery system. Possibility of optimization of the output capacitors bank in relation to the RMS value of the current ripple is investigated.
TL;DR: In this paper, a stable colloidal tetrapropylammonium manganese oxide (TPA-MO) was formed by the reduction of tetraplampyramide permanganate with 2-butanol at room temperature.
Abstract: Stable colloidal tetrapropylammonium manganese oxide ~TPA-MO! was formed by the reduction of tetrapropylammonium permanganate with 2-butanol at room temperature. Thin films of TPA-MO were prepared using the sol-gel process by dip-coating directly onto clean nickel foils followed by heat-treatment under controlled conditions. The microstructure evolution of TPA-MO films at various calcination temperatures was characterized using Brunauer-Emmett-Teller method, X-ray diffraction, and scanning electron microscopy. The performance of these films as supercapacitors was evaluated using cyclic voltammetry in various aqueous electrolytes. These thin films exhibited excellent capacitive behavior with a specific capacitance of 720 F/g. These films also showed good reversibility and cycling stability, losing little more than 20% of their charge capacity after 1500 cycles.
TL;DR: In this article, different modifications of multiwalled carbon nanotubes (MWNTs) have been performed to increase specific capacitance of this material for supercapacitor application.
TL;DR: In this article, activated carbon nanotubes (CNTs) were produced by KOH and used as the electrochemical super capacitors (ESCs) electrode materials, and they were both examined by transmission electron microscopy, scanning electric microscopy (SEM), and X-ray diffraction (XRD).
TL;DR: In this paper, the dependence of impedance parameters on direct current (nonlinearity), temperature, state-of-charge, and previous discharge/charge regime is investigated, and it is shown that model parameters extracted from the impedance spectra are closely linked with the charge-transfer kinetics, double-layer capacitance, transport limitation, and porous structure of the electrodes.
TL;DR: In this article, an asymmetric hybrid energy storage device was built using a lithium titanate intercalation anode and the pseudocapacitive electronically conducting polymer poly(fluorophenythiophene).
Abstract: An asymmetric hybrid energy storage device has been built using a lithium titanate intercalation anode and the pseudocapacitive electronically conducting polymer poly(fluorophenythiophene). Results show that the device operates in the power range of electrochemical double-layer capacitors, while having three to four times their energy density, and a voltage profile and self-discharge characteristics typical of a battery. The cycle life is also intermediate between that of a battery and a supercapacitor, in the range of several thousands of cycles.
TL;DR: In this paper, the impact of current amplitude and pulse duty on the specific power and energy storage capacities of Li-ion batteries, ultracapacitors, and parallel combinations of these devices were characterized with respect to their ability to meet the power demands of pulsed loads.
TL;DR: In this article, a polyaniline powder doped with LiPF 6 was used as an electrode material in a polymer redox supercapacitor and the electrode sheet was fabricated by coating the slurry directly on a charge collector.
TL;DR: In this paper, the crystalline structure, morphology and the electrochemical properties of the electrodes have been studied as a function of the annealing temperature, and they have been found to perform well in electrochemical capacitor applications with a specific capacitance close to 550 F g � 1.
TL;DR: In this article, the effect of substrate properties on capacitance of PANI/SS electrodes has been evaluated by assembling symmetrical capacitors and subjecting them to galvanostatic charge/discharge cycles between 0 and 0.75 V.
Abstract: Polyaniline (PANI) has been studied as an active material for electrochemical capacitors. Polymerization of aniline to PANI has been carried out potentiodynamically on a stainless steel (SS) substrate, instead of Pt-based substrates generally employed for this application. The PANI/SS electrodes have been evaluated by assembling symmetrical capacitors in NaClO(4) + HClO(4) mixed electrolyte and subjecting them to galvanostatic charge/discharge cycles between 0 and 0.75 V. The effect of substrate has been assessed by comparing the capacitance of PANI/SS and PANI/Pt electrodes. The capacitance of PANI/SS electrode is higher than that of PANI/Pt electrode by several times. The effect of sweep rate of potentiodynamic deposition of PANI/SS on capacitance has been investigated. At a power density of 0.5 kW kg(-1), a capacitance value of 815 F g(-1) of PANI is obtained for the deposition sweep rate of 200 mV s(-1). Increase in thickness of PANI on the SS substrate results in an increase in capacitance of PANI. This value of capacitance is the highest ever reported for any electrochemical capacitor material. Thus, in addition to a favorable economic aspect involved in using SS instead of Pt or Pt-based substrate, the advantage of higher capacitance of PANI has also been achieved. (C) 2002 The Electrochemical Society.
TL;DR: In this article, polyaniline (PANI) has been potentiodynamically deposited on stainless steel substrate and characterized in a gel polymer electrolyte (GPE), which facilitates a voltage limit of the capacitor to 1 V instead of 0.75 V in aqueous electrolytes.
Abstract: Studies on redox supercapacitors employing electronically conducting polymers are of great importance for hybrid power sources and pulse power applications. In the present study, polyaniline (PANI) has been potentiodynamically deposited on stainless steel substrate and characterized in a gel polymer electrolyte (GPE). Use of the GPE facilitates a voltage limit of the capacitor to 1 V, instead of 0.75 V in aqueous electrolytes. From charge-discharge studies of the solid-state PANI capacitors, a specific capacitance of 250 F g(-1) has been obtained at a specific power of 7.5 kW kg(-1) of PANI. The values of specific capacitance and specific power are considerably higher than those reported in the literature. High energy and high power characteristics of the PANI are presented. (C) 2002 The Electrochemical Society.
TL;DR: In this paper, an all-solid-state supercapacitor is fabricated and optimized using a Nafion® membrane and an ionomer, which exhibits a relatively stable capacitance during l0,000 cycles of operation.
Patent•
14 May 2002
TL;DR: In this paper, a high current pulse generator for DC powered devices is presented, which includes batteries as the power source that charges supercapacitors as well as provides power to the loads as required.
Abstract: The present invention provides a high current pulse generator for DC powered devices. The generator includes batteries as the power source that charges supercapacitors as well as provides power to the loads as required. During charging, the supercapacitors are connected in parallel, but they are switched to series connection by relays at the moment that the loads demand large currents. No other controlling means except for relays in the circuit is employed, so that the electric arrangement is simple, reliable, and cost-effective. As the batteries are designed to deliver currents at low discharge rates, the effective use-time of batteries is prolonged. Furthermore, due to the high power densities of supercapacitors, the readily available alkaline batteries can be utilized in the power unit for electric power tools.