Showing papers on "Supercapacitor published in 2005"
TL;DR: In this paper, the capacitance values for the composites strongly depend on the cell construction and applied voltage was found to be the key factor influencing the specific capacitance of nanocomposites.
708 citations
TL;DR: In this article, the specific capacitance and the hydrogen adsorption capacity in the carbon nanopores were correlated with the microtextural properties, and a linear dependence has been found between the capacitance or the amount of electrochemically stored hydrogen and the ultramicropores (pores smaller than 0.7nm).
657 citations
TL;DR: In this paper, mesoporous carbons with tailored pore size distribution are used as electrodes for supercapacitors and the design of their pore sizes allows suiting the dimensions of electrolyte ions and efficient charging of the electrical double layer.
390 citations
TL;DR: In this article, carbon nanotubes (CNTs) are proposed as an alternative additive of carbon black for improving the electrical conductivity of the manganese oxide electrodes used to build capacitors.
Abstract: Nanocrystalline metal oxides can be prepared with large surface area, electrochemical stability, and pseudocapacitive behavior, being able to be used as supercapacitor electrodes. Among the various metal oxides studied, amorphous and hydrated manganese oxide (a-MnO 2 .nH 2 O) is the most promising for supercapacitor electrodes due to the low cost of the raw material. In the present work, amorphous manganese dioxide (a-MnO 2 .nH 2 O) is prepared by chemical co-precipitation of Mn(VII) and Mn(II) in water medium, giving small particles of relatively high surface area. Carbon nanotubes (CNTs) are proposed as an alternative additive of carbon black for improving the electrical conductivity of the manganese oxide electrodes used to build capacitors. The results demonstrate that CNTs are effective for increasing the capacitance and improving the electrochemical properties of the a-MnO 2 .nH 2 O electrodes which show a better capacitive behavior than with carbon black. This enhancement is due to the high entanglement of CNTs which form a network of open mesopores, allowing the bulk of MnO 2 to be easily reached by the ions. The performance optimization requires a careful control of the electrolyte pH in order to avoid the irreversible reactions Mn(IV) to Mn(II) at the negative electrode and Mn(IV) to Mn(VII) at the positive one.
364 citations
TL;DR: In this paper, a surface treatment for Al current collector foil via the sol-gel route has been used in order to decrease the Al/active material interface resistance, and the results obtained with 4 cm2 carbon/Carbon supercapacitors cells in organic electrolyte.
330 citations
TL;DR: In this paper, a series of carbons with similar microtextural characteristics (SBET about 800m2/g, micropore fraction 0.84-0.93) were tested for supercapacitor application.
328 citations
TL;DR: In this paper, a hybrid electrochemical surpercapacitor was proposed in which activated carbon was used as a negative electrode and a lithium-ion intercalated compound LiMn2O4 as a positive electrode in a mild Li2SO4 aqueous electrolyte.
289 citations
TL;DR: In this article, a form of thin films formed by multi-walled carbon nanotubes exhibiting high packing density and local alignment were fabricated using a highly concentrated colloidal suspension of carbon nanotsubes.
Abstract: An ew form of thin films formed by multi-walled carbon nanotubes exhibiting high packing density and local alignment were fabricated using a highly concentrated colloidal suspension of carbon nanotubes. Electrical double layer capacitors built from these film electrodes exhibited a close to rectangular cyclic voltammogram even at a high scan rate of 1000 mV s −1 , an dp roduced very high specific power density of about 30 kW kg −1 ,i deal for surge-power delivery applications. The preparation procedure is very simple, and does not require any binders. It has potential for highly efficient manufacturing of high power density supercapacitors and other similar electronic devices.
280 citations
TL;DR: In this paper, an asymmetric supercapacitor with RuO2/TiO2 nanotube composite was used as positive electrode and activated carbon as negative electrode in 1/mol/L KOH electrolyte solution.
279 citations
TL;DR: In this paper, the authors have fabricated supercapacitor electrodes with nickel oxide (NiO)/carbon nanotubes (CNTs) nanocomposite formed by a simple chemical precipitation method.
229 citations
TL;DR: In this paper, a nonaqueous hybrid supercapacitor using manganese oxide/MWNTs (M/M) composite and MWNTs as positive and negative electrodes, respectively, has been designed and investigated by constant current charge/discharge tests.
TL;DR: In this article, the performances of 4 cm 2 supercapacitors cells assembled with 200mm thick active material films composed with activated carbon and carbon nanotubes mixture in organic electrolyte have been carried out.
TL;DR: In this paper, a manganese dioxide was electrochemically deposited on a Ni substrate from a neutral electrolyte in the presence of a surface-active agent, namely, sodium lauryl sulfate ~SLS!, for supercapacitor application.
Abstract: Manganese dioxide has been electrochemically deposited on a Ni substrate from a neutral electrolyte in the presence of a surface-active agent, namely, sodium lauryl sulfate ~SLS!, for supercapacitor application. The potentiodynamically prepared oxide provides higher capacitance than the potentiostatically and galvanostatically prepared oxides. Owing to adsorption of the surfactant molecules at the interface during electrodeposition, the manganese dioxide possesses higher specific surface area. Specific capacitance of 310 F g−1 obtained for the oxide prepared in the presence of SLS over an extended charge-discharge cycling is higher by about 25% in relation to the oxide prepared in the absence of SLS. © 2005 The Electrochemical Society. @DOI: 10.1149/1.1922869# All rights reserved.
TL;DR: In this article, a polyaniline-coated carbon nanofiber was fabricated using one-step vapor deposition polymerization technique, and the specific capacitance was shown to have a maximum value of 264 F/g when the thickness was ca. 20 nm.
TL;DR: In this article, the double layer capacity of pyrrole treated-functionalized single wall carbon nanotubes (SWNTs) was shown to be 154 μF/cm2 based on the BET model, and even higher based on DFT model.
Abstract: Supercapacitor electrodes based on pyrrole treated-functionalized single wall carbon nanotubes (SWNTs) were developed. High values of capacitance (350 F/g), power density (4.8 kW/kg), and energy density (3.3 kJ/kg) were obtained in 6 M KOH, and the capacitance is almost 7 times that of the control buckypaper. Specific capacitance of these materials has a strong dependence on the macropore surface area. The double layer capacity of pyrrole treated-functionalized SWNT electrodes is 154 μF/cm2 based on the BET model, and even higher based on the DFT model.
TL;DR: In this article, an electrochemical investigation into properties of hydrous MnO 2 grown by electrodeposition from aqueous solution was conducted and the authors observed a consistent insensitivity in specific capacitance for material deposited under potentiostatic conditions at 1.5 V in comparison to galvanostatic depositions occurring in the 0.55 V range.
TL;DR: In this paper, four samples of carbon black were synthesized for use in aqueous supercapacitors and their capacitance was measured at room temperature and at −40°C, using slow sweep cyclic voltammetry.
TL;DR: In this article, a solvent-free green electrolyte for high-voltage hybrid supercapacitors was developed, and the cyclability of a laboratory scale cell with electrode mass loading sized for practical uses was tested at 60°C over 16,000 galvanostatic charge-discharge cycles at 10 µm −2 in the 1.5 and 3.6 µm voltage range.
TL;DR: In this article, a new form of nanofibre web electrode has been fabricated for a supercapacitor using electrospun polybenzimidazol (PBI)-based activated carbon nanofibrres.
06 Mar 2005
TL;DR: In this article, the three major factors determining proton exchange membrane (PEM) fuel cell power system dynamic performance, hydration/temperature, compressor time constant, and bulk energy storage are analyzed.
Abstract: This paper intends to serve as a guide for the interactions between the power conditioning system and the fuel cell. The three major factors determining proton exchange membrane (PEM) fuel cell power system dynamic performance, hydration/temperature, compressor time constant, and bulk energy storage are analyzed. The notion of multiple fuel cell time constants is introduced and derived. The various operating points of a fuel cell, ripple current mitigation and energy balance are illustrated with experimental data. Individual time constant validation techniques are offered and different capacitor bulk storage strategies (including ultra capacitors) are analyzed. A complete single phase power conditioning system is presented with experimental waveforms that can apply to different systems
TL;DR: In this paper, highly dispersed RuO2 nanoparticles were obtained on carboxylated carbon nanotubes by preventing agglomeration among RuO 2 nanoparticles by bond formation.
Abstract: To enhance its pseudocapacitance, ruthenium oxide must be formed with a hydrated amorphous and porous structure and a small size, because this structure provides a large surface area and forms conduction paths for protons to easily access even the inner part of the RuO2 In this study, we report that highly dispersed RuO2 nanoparticles could be obtained on carboxylated carbon nanotubes This could be achieved by preventing agglomeration among RuO2 nanoparticles by bond formation between the RuO2 and the surface carboxyl groups of the carbon nanotubes Highly dispersed RuO2 nanoparticles on carbon nanotubes showed an increased capacitance, which can be explained by the fact that with the decrease in size protons were able to access the inner part of RuO2, so that its utilization was increased The high dispersion of RuO2 is therefore a key factor to increase the capacitance of nanocomposite electrode materials for supercapacitors
TL;DR: In this article, a new process was presented for synthesizing the supercapacitor electrodes of carbon aerogel via pyrolyzing resorcinol-formaldehyde (RF) aerogels, which could be costeffectively obtained by ambient drying of wet RF-gels instead of conventional supercritical drying.
Abstract: A new process is presented for synthesizing the supercapacitor electrodes of carbon aerogel via pyrolyzing resorcinol-formaldehyde (RF) aerogel, which could be cost-effectively obtained by ambient drying of wet RF-gels instead of conventional supercritical drying. Defect free RF-aerogels instead of conventional supercritical drying. Defect free RF-aerogels with the linear shrinkage of less than 8% could be manufactured by ambient-drying of wet RF-gels. Carbon aerogels with high strength were prepared via pyrolyzing RF-aerogels in N2 atmosphere. The specific surface area (< 600 m2/g) and the electrical conductivity (∼ 50 S/cm) of carbon aerogels varied in sensitivity with the pyrolysis condition, while their densities (0.6 g/cm3) and porosities (70%) were found to be almost constant. Post heat-treatment of carbon aerogels around 300^∘C in air atmosphere was very effective for improving the electrochemical properties of electrodes. The carbon aerogel electrode pyrolyzed at 800∘C showed the specific capacitances of about 40 F/g in H2SO4 electrolyte solution and 35 F/g in KOH solution.
TL;DR: In this article, the polyaniline (PANI) was used as an electroactive material in supercapacitors and the performance of PANI was investigated by cyclic voltammetry, a galvanostatic charge-discharge test and electrochemical impedance spectroscopy.
Abstract: The polyaniline (PANI) prepared by the pulse galvanostatic method (PGM) or the galvanostatic method on a stainless steel substrate from an aqueous solution of 0.5 mol/l H2SO4 with 0.2 mol/l aniline has been studied as an electroactive material in supercapacitors. The electrochemical performance of the PANI supercapacitor is characterized by cyclic voltammetry, a galvanostatic charge–discharge test and electrochemical impedance spectroscopy in NaClO4 and HClO4 mixed electrolyte. The results show that PANI films with different morphology and hence different capacitance are synthesized by controlling the synthesis methods and conditions. Owing to the double-layer capacitance and pseudocapacitance increase with increasing real surface area of PANI, the capacitive performances of PANI were enhanced with increasing real surface area of PANI. The highest capacitance is obtained for the PANI film with nanofibrous morphology. From charge–discharge studies of a nanofibrous PANI capacitor, a specific capacitance of 609 F/g and a specific energy density of 26.8 Wh/kg have been obtained at a discharge current density of 1.5 mA/cm2. The PANI capacitor also shows little degradation of capacitance after 1,000 cycles. The effects of discharge current density and deposited charge of PANI on capacitance are investigated. The results indicate that the nanofibrous PANI prepared by the PGM is promising for supercapacitors.
TL;DR: In this paper, a hybrid type electrochemical capacitor was made and tested, in which the activated-carbon loaded with nickel oxide was used as cathode material and activated carbon used as anode material.
TL;DR: In this paper, a microstructural and mathematical analysis for the characterization of a relatively high specific energy supercapacitor is provided, which allows one to determine the optimal target operating voltage for hybrid vehicle operation, calculate the available energy vs. available power for the system, and clarify the electrode utilization through the examination of the stored charge as a function of position.
Abstract: For hybrid-electric vehicle applications, supercapacitors show promise for providing low cost per unit power, high-efficiency energy storage, substantially temperature-invariant operation, and high cycle life (potentiallyequating to one supercapacitor pack per vehicle lifetime). Here we provide a microstructural and mathematical analysis for the characterization of a relatively high specific energy supercapacitor. The governing equations and the boundary conditions are generalized so that the cell can be modeled using a current, potential, or power excitation source. An Appendix clarifies the role of binary-electrolyte diffusion. The overall analysis allows one to determine the optimal target operating voltage for hybrid vehicle operation, calculate the available energy vs. available power for the system, and clarify the electrode utilization through the examination of the stored charge as a function of position.
TL;DR: In this paper, the ruthenium oxide was electrodeposited onto a carbon nanotube (CNT) film substrate with a three-dimensional porous structure at the nanometer scale.
Abstract: Ruthenium oxide was electrodeposited onto a carbon nanotube (CNT) film substrate with a three-dimensional porous structure at the nanometer scale. For comparison, ruthenium oxide was prepared on a Pt plate and carbon paper substrate. Microstructures of the ruthenium oxide-based electrodes examined by scanning and transmission electron microscopy showed that the ruthenium oxide layers (∼3 nm thickness) were electrochemically deposited on the surface of the multiwalled CNT. The ruthenium oxide on CNT film substrate showed not only a much higher specific capacitance of 1170 F/g, but also an improved rate capability, compared with the ruthenium oxide layers on a Pt plate and carbon paper substrate. The improved specific capacitance and rate capability of ruthenium oxide on CNT film substrate are attributed to its electrode construction comprising a very thin film of the electroactive material on a conductive CNT film substrate with a three-dimensional nanoporous structure.
TL;DR: In this paper, the authors compared the electrochemical properties of as-prepared and activated carbon nanofibres with those of a commercial sample; the latter was activated by the same way as our sample.
TL;DR: In this article, the application of ultrasonic irradiation in preparing conducting polymer as active material for supercapacitor was studied, and the specific capacitance of poly(3,4-ethylenedioxythiphene) (PEDOT) with 1 M H 2 SO 4 as supporting electrolyte was shown to increase from 72 to 100 F/g.
TL;DR: In this article, the authors proposed a hybrid electrochemical supercapacitor which relies on two different electrode materials, Li4Ti5O12 and active carbon, which showed a higher power density and a corresponding cycle life.
Abstract: Supercapacitors coupled with batteries and fuel cells are considered promising midterm and long-term solutions for low- and zeroemission transport vehicles by providing the power peaks for startstop, acceleration, and recovering the breaking energy. Nowadays, much research on the electrochemical capacitors aim to increase power and energy density as well as lower fabrication costs and at the same time focus on making environmentally friendly materials. Compared with the traditional electrochemical double-layer capacitor EDLC, the hybrid electrochemical supercapacitor which relies on two different electrode materials shows a higher power density and a corresponding cycle life. This was recently reported by Telcordia Technologies with a new device named nonaquous asymmetric hybrid electrochemical supercapacitor HBEC with an intercalation compound Li4Ti5O12 which was used as the negative material and active carbon which was used as the positive material. 1 The new