Showing papers on "Supercapacitor published in 2000"

Supercapacitor electrodes from multiwalled carbon nanotubes

Abstract: Electrochemical characteristics of supercapacitors built from multiwalled carbon nanotubes electrodes have been investigated and correlated with microtexture and elemental composition of the materials. Capacitance has been estimated by cyclovoltammetry at different scan rates from 1 to 10 mV/s, galvanostatic discharge, and impedance spectroscopy in the frequency range from 100 kHz to 1 mHz. The presence of mesopores due to the central canal and/or entanglement is at the origin of an easy accessibility of the ions to the electrode/electrolyte interface for charging the electrical double layer. Pure electrostatic attraction of ions as well as quick pseudofaradaic reactions have been detected upon varying surface functionality. The values of specific capacitance varied from 4 to 135 F/g, depending on the type of nanotubes or/and their posttreatments. Even with moderate specific surface area (below 470 m2/g), due to their accessible mesopores, multiwalled carbon nanotubes represent attractive materials for su...

Rechargeable hybrid battery/surpercapacitor system

Abstract: A rechargeable hybrid battery/supercapacitor electrical storage system capable of providing high energy and high power densities comprises an intercalation electrode (17) and a capacitor electrode (13) combined with a separator (15) and electrically-conductive current collector elements (11, 19) to form a unitary cell structure (10). An electrolyte solution of a dissociable salt absorbed into the porous structure of the separator (15) provides complementary ion species which respectively reversibly intercalate into the one electrode (17) and capacitively adsorb at the surface of the other electrode (13) upon the application of charging current. The high density stored electrical energy may be recovered at high power over extended periods upon demand of a utilizing device and may be rapidly restored to stable capacity through numerous charging cycles.

Properties and applications of supercapacitors From the state-of-the-art to future trends

Abstract: Electrochemical double-layer capacitors, also known as supercapacitors or ultracapacitors, are electrical storage devices, which have a relatively high energy storage density simultaneously with a high power density. Recent developments in basic technology, materials and manufacturability have made supercapacitors an imperative tool for shortterm energy storage in power electronics. With much higher energy density than today's capacitors and none of the problems associated with conventional battery technology, supercapacitors give an access to new power electronic and industrial storage applications.

Polymer Selection and Cell Design for Electric‐Vehicle Supercapacitors

Abstract: Supercapacitors are devices for applications requiring high operating power levels, such as secondary power sources in electric vehicles (EVs) to provide peak power for acceleration and hill climbing. While electronically conducting polymers yield different redox supercapacitor configurations, devices with the n-doped polymer as the negative electrode and the p-doped polymer as the positive one are the most promising for EV applications. Indeed, this type of supercapacitor has a high operating potential, is able to deliver all the doping charge and, when charged, has both electrodes in the conducting (p- and n-doped) states. This study reports selection criteria for polymer materials and cell design for high performance EV supercapacitors and experimental results of selected polymer materials.

A physical based model of power electric double-layer supercapacitors

Abstract: Recent developments in the field of supercapacitors have led to the achievement of high specific energy and high specific power devices. Due to capacitances of several hundred farads and serial resistances of less than one milliohm, these new components are suitable for energy storage in high power electronic applications, especially in the field of management of embarked electrical power (hybrid power sources, energy recovery). This paper presents the theory, characterisation and experimental validation of an accurate electric double-layer supercapacitor model based on the physics of phenomena governing charges storage, which theoretically leads to a transmission line with voltage dependant distributed capacitance.

Mesoporous carbon material, carbon/metal oxide composite materials, and electrochemical capacitors using them

Abstract: The present invention is related to carbon materials having 2-20nm of mesopore and high porosity, carbon/metal oxide composites which are prepared with said material and wherein metal oxides are deposited in the pores, electrical double-layer capacitors prepared with said carbon material, and electrochemical capacitors prepared with said carbon/metal oxide composite. When the mesoporous carbon is used as an electrode material of electrical double-layer capacitors, in spite of low capacitance value per weight for low surface area, said electrical double-layer capacitor has higher charge storage volume than the previous ones due to low equivalent series resistance. Furthermore, when said carbon/metal oxide composite is used as an electrode material of electrical double-layer capacitor, the capacitor has high capacitance value per unit weight, i.e., 254 F/g, by combining the electrical double-layer capacitor with the pseudo capacitor from the metal oxide.

A physical based model of power electric double-layer supercapacitors

Abstract: Recent developments in the field of supercapacitors have led to the achievement of high specific and high power density devices. With capacities of several hundred farads and serial resistances less than one milliohm, these new components are suitable for energy storage in high power electronic applications, especially in the field of management of embarked electrical power (hybrid power sources, energy recovery). This paper deals with investigations, including theory, characterisation and experimental validation, on an accurate electric double-layer supercapacitor modelling based on the physics of phenomena governing charges storage, which theoretically leads to a transmission line with voltage dependant distributed capacitance.

Method for preparing nanoporous carbon materials and electric double-layer capacitors using them

Abstract: Disclosed herein is the fabrication method of producing nanoporous carbon materials with pore sizes ranging from 2 nanometer to 20 nanometer which can be used as electrode materials for a supercapacitor and an electric double layer capacitors being a kind of supercapacitor. The invention also relates to electric double layer capacitors utilizing these carbon materials as electrodes. The carbon materials presented in the present invention possess regular pores with dimensions ranging in between 2 nm and 20 mm and exhibit high electrical conductivity. These carbon materials shows low equivalent series resistance (ESR) and thus exhibits high charge storage capacity at high charging/discharging current density.

Electrochemical impedance characterisation of a nanostructured (mesoporous) platinum film

Abstract: Nanostructured platinum films with an hexagonal array of uniform, regularly-sized pores were grown on platinum substrates by electrochemical plating from a liquid crystalline electrolyte. The films were characterised as models for nanoporous electrodes, first by cyclic voltammetry in dilute sulfuric acid, showing enhanced currents due to the internal area of the pore structure. Complex impedance spectroscopy was then used to determine the access time of the capacitance and pseudocapacitance in the double layer and hydrogen adsorption regions, respectively. The results were analysed in terms of a transmission line model, showing capacitance at low frequencies and diffusive behaviour above 1 kHz. Capacitance values were as expected from the internal surface area and in agreement with the cyclic voltammetry results. The pore resistance was higher than predicted from a straight pore model, and showed apparent tortuosity factors of about 10. Nevertheless, the nanostructured material gave a very impressive performance as a supercapacitor, with a volumetric capacitance of 110 F cm−3 and an effective diffusion coefficient of 5 × 10−5 cm2 s−1 in the double layer region.

High energy density hybrid battery/supercapacitor system

Abstract: A rechargeable hybrid battery/supercapacitor electrical storage system capable of providing high energy and high power densities comprises a negative intercalation electrode ( 17 ) and a positive capacitor electrode ( 13 ) comprising an anion-adsorbing component and a cation-intercalating material combined with a separator ( 15 ) and electrically-conductive current collector elements ( 11, 19 ) to form a unitary cell structure ( 10 ). An electrolyte solution of a dissociable salt absorbed into the porous structure of the separator ( 15 ) provides complementary ion species which, supplemented by cations supplied from the positive electrode intercalation material in order to increase the energy density capability of the system, respectively reversibly intercalate into the negative electrode ( 17 ) and capacitively adsorb at the surface of the positive electrode ( 13 ) upon the application of charging current. The high density stored electrical energy may be rapidly recovered at high power over extended periods upon demand of a utilizing device and may be equally rapidly restored to stable high energy capacity through numerous charging cycles.

Capacitors and supercapacitors containing modified carbon products

Abstract: Capacitors, including supercapacitors, are described wherein the electrode contains at least one modified carbon product, wherein the modified carbon product is at least one carbon product having attached at least one organic group. The use of the modified carbon product in the electrodes for capacitors preferably leads to improved capacitance and/or lower internal resistance of the capacitor. Further, the use of modified carbon products in the electrodes for capacitors permits easier manufacturing steps for the production of capacitors.

An improved method for controlling an EDLC-battery hybrid stand-alone photovoltaic power system

Abstract: Stand-alone photovoltaic power systems are potential power sources for wireless and optical telecommunications equipment and solar home systems. For these systems to be practical, the batteries used to store the power must have a long lifetime. We have proposed a stand-alone photovoltaic power system that uses an electric double-layer capacitor (EDLC) with lead-acid batteries. This system reduces the number of battery charge-and-discharge cycles and maintains the optimal charging voltage by using EDLC discharge power. In this paper, we describe the system's circuit configuration, operation, and conversion efficiency analysis. An improved method is described for controlling the system. It increases the system's power-conversion efficiency by keeping the capacitor voltage high. Simulation of a 250 W photovoltaic system showed that it reduces the power conversion losses in the system by about 35%.

Metal oxide electrode for supercapacitor and manufacturing method thereof

Abstract: A metal oxide electrode for a supercapacitor and a manufacturing method thereof are disclosed. Potassium permanganate is absorbed on a conductive material, such as carbon or activated carbon, and mixed with a solution including manganese acetate so as to form amorphous manganese oxide. Amorphous manganese oxide powder is grounded to a powder which is mixed with binder to form an electrode having a predetermined shape. The electrode reduces equivalent serial resistance and enhances high frequency characteristics since the contact area and the adhesion strength between the manganese oxide and the conductive carbon are improved. Also, the electrode has high capacitance suitable for a supercapacitor, which is manufactured therefrom at a greatly reduced cost.

The Development of Carbon Nanotubes/RuO2·xH2O Electrodes for Electrochemical Capacitors

Abstract: Carbon nanotubes were refluxed with nitric acid to create acid sites on the surface. After such treatment, amorphous or nano-scale crystalline RuO2·xH2O can be adhered to the surfaces of carbon nanotubes by a simple method. RuO2·xH2O became more amorphous with decreasing the fraction of carbon nanotubes. The capacitance can be enhanced significantly by the adherence. When the weight fraction of RuO2·xH2O in the composite electrodes reached 75%, a specific capacitance of 560 F g-1 was achieved. On the other hand, carbon nanotubes/RuO2·xH2O capacitors exhibit excellent power delivery behavior. So the processing of carbon nanotubes/RuO2·xH2O composite electrodes is a new attempt to fabricate supercapacitors with both high energy and high power density.

Transient analysis of pulsed charging in supercapacitors

Abstract: Transient voltage/current pulses cannot be stored into normal DC batteries. This work reviews possibility of storing these surges using supercapacitor. Laser induced plasma may be caused by firing laser pulses into the clouds charge clusters. The charge pulses flow down along the laser induced air wire (LIAW) and passes through a supercapacitor to charge it. Objective of this study is to test the possibility of storing these charges using supercapacitors. Energy storage in solid state electrochemical capacitors (supercapacitors) or ultra supercapacitors occurs through reversible oxidation-reduction (redox) reactions. Contribution of double layer is less significant, however, a major percentage of total energy stored is attributed to reversible surface redox reactions. Different types of supercapacitors have been analyzed regarding their charge and discharge performance under repetitively charging pulses. The authors' initial analysis based on existing mathematical techniques, shows that a real superconductor may charge under transient conditions at a much higher rate but subsequent considerations based on mathematical analysis and available data on supercapacitors technology, lead us to new recommendations to improve the design of supercapacitor to perform as an ultrasupercapacitor.

Supercapacitors electrical behaviour for power electronics applications

Abstract: Recent developments in the field of supercapacitors have led to the achievement of high specific energy and high specific power devices. Due to capacitances of several hundred farads and serial resistances of less than one milliohm, these new components are suitable for energy storage in high power electronic applications, especially in the field of management of embarked electrical power (hybrid power sources, energy recovery). This paper presents theory, characterisation and experimental validation of an accurate electric double-layer supercapacitor model based on the physics of phenomena governing charges storage, which theoretically leads to a transmission line with voltage dependant distributed capacitance.

Modifications to a hydrogen/electric hybrid bus

Abstract: A program to modify a hydrogen hybrid electric bus is described. This is an electric bus that uses a hydrogen-fueled internal combustion engine to charge on-board batteries. The primary goal of the reported work is to extend the range of the bus in a cost-effective manner. Among the modifications being made are the development of a new engine, upgrading the power control system, rewiring critical elements, adapting a supercapacitor regenerative braking system, devising more effective changes to the hydrogen safety systems, and adding a high pressure gas storage system to supplement the existing hydride bed hydrogen storage. All of this work is being supplemented with the use of a dynamic simulation code to determine optimal operational strategies.

Use of activated carbon in electrodes for electric double-layer capacitors and electrodes for electric double-layer capacitors.

Abstract: Activated carbon obtained by activating a carbonaceous material is processed with an acid at an elevated temperature. The acid-processed activated carbon has a strong affinity for water, and is favorable to water purification. Electrodes produced by shaping the acid-processed activated carbon have the advantage of large electrostatic capacity per unit volume, and are favorable for capacitors.

Evaluation of solid polymer electrolytes for use in conducting polymer/nanotube actuators

Abstract: The stringent requirements for a solid polymer electrolyte (SPE) in solid state devices such as batteries or supercapacitors are even more demanding when used in electromechanical actuators. Not only is the SPE expected to exhibit good conductivity, mechanical properties, adhesion and mechanical/electrical stability, but it must also be flexible, maintained good adhesion while flexing, be easily processible and be able to function in air. In this work polyacrylonitrile and Kynar based non-aqueous SPEs and water based polyacrylamide hydrogel ion source/sinks containing various perchlorate salts were tested for their applicability to polypyrrole and carbon nanotube actuators and supercapacitors. The results indicate that the optimum SPE for both polypyrrole and carbon nanotube actuators would be a polyacrylonitrile plasticized with propylene carbonate and ethylene carbonate containing 1.0M NaClO4. It is also apparent that the same SPE would be the most suitable for supercapacitor applications with these materials.

Development of Carbon-Metal Oxide Supercapacitors from Sol-Gel Derived Carbon-Ruthenium Xerogels.

Abstract: There has been increasing interest in electrochemical capacitors as energy storage systems because of their high power density and long cycle life, compared to battery devices. According to the mechanism of energy storage, there are two types of electrochemical capacitors. One type is based on double layer (dl) formation due to charge separation, and the other type is based on a faradaic process due to redox reactions. Sol-gel derived high surface area carbon-ruthenium xerogels were prepared from carbonized resorcinol-formaldehyde resins containing an electrochemically active form of ruthenium oxide. The electrochemical capacitance of these materials increased with an increase in the ruthenium content indicating the presence of pseudocapacitance associated with the ruthenium oxide undergoing reversible faradaic redox reactions. A specific capacitance of 256 F/g (single electrode) was obtained from a carbon xerogel containing 14 wt% Ru, which corresponded to more than 50% utilization of the ruthenium. The double layer accounted for 40% of this capacitance. This material was also electrochemically stable, showing no change in a cyclic voltammogram for over 2,000 cycles.

Development of supercapacitors based on carbon nanotubes

Abstract: Block-type electrodes made of carbon nanotubes were fabricated by different processes. The volumetric specific capacitance based on such electrodes reached 107 F/cm3, which proves carbon nanotubes to be ideal candidate materials for supercapacitors. The composite electrodes consisting of carbon nanotubes and RuO2·xH2O were developed by the deposition of RuO2 on the surface of carbon nanotubes. Supercapacitors based on the composite electrodes show much higher specific capacitance than those based on pure carbon nanotube ones. A specific capacitance of 600 F/g can be achieved when the weight percent of RuO2·xH2O in the composite electrodes reaches 75%. In addition, supercapacitors based on the composite electrodes show both high energy density and high power density characteristics.

New materials for batteries and fuel cells. Materials Research Society symposium proceedings, Volume 575

Abstract: This proceedings volume is organized into seven sections that reflect the materials systems and issues of electrochemical materials R and D in batteries, fuel cells, and capacitors The first three parts are largely devoted to lithium ion rechargeable battery materials since that electrochemical system has received much of the attention from the scientific community Part 1 discusses cathodes for lithium ion rechargeable batteries as well as various other battery systems Part 2 deals with electrolytes and cell stability, and Part 3 discusses anode developments, focusing on carbon and metal oxides Part 4 focuses on another rechargeable system that has received substantial interest, nickel/metal hydride battery materials The next two parts discuss fuel cells--Part 5 deals with Proton Exchange Membrane (PEM) fuel cells, and Part 6 discusses oxide materials for solid oxide fuel cells The former has the benefit of operating around room temperature, whereas the latter has the benefit of operating with a more diverse (non-hydrogen) fuel source Part 7 presents developments in electrochemical capacitors, termed Supercapacitors These devices are receiving renewed interest and have shown substantial improvements in the past few years In all, the results presented at this symposium gave a deeper understanding of the relationship between synthesis,more » properties, and performance of power source materials Papers are processed separately for inclusion on the data base« less

Resorcinol-formaldehyde-derived carbon aerogel films

Abstract: Carbon aerogels derived from organic sol-gel process and supercritical drying are novel porous materials with interconnect structures and higher electrical conductivity, which are considered to be ideal electrode materials for supercapacitors and rechargeable batteries. The objective of the research was to synthesize carbon aerogel films at ambient conditions. Resorcinol formaldehyde (RF) and carbon aerogel films have been produced with extremely high RC ratio (molar ratio of resorcinol to catalyst) followed by subcritical drying. The structure of the porous films was investigated using electron scanning microscope. The specific surface area was measured by using nitrogen adsorption and electrical conductivity was measured with four-probe method. It was found that with extremely high RC ratio, the porous structure of RF and carbon aerogel films can be controlled from micro to macro porous at ambient conditions. With respect to the application as electrodes for full cells, carbon aerogel films with different porous structures on the two surfaces have been also obtained through optimizing the sol-gel process.

5 – Battery/fuel-cell EV design packages

Abstract: Publisher Summary This chapter describes some of the electric batteries: advanced lead acid, sodium–sulfur, Nickel–metal hydride, sodium chloride/nickel, and lithium ion. The super capacitor will be an important contributor to the energy efficient hybrid vehicle, the absence of chemical reaction allowing a durable means of obtaining high-energy charge/discharge cycles. Flywheel energy storage systems for use in vehicle propulsion have reached application in the light tram vehicle. Motor control alternatives such as parallel/series rheostatic control, or weak field control, can be better for certain applications, but the more elaborate thyristor, chopper, control of motor with respect to battery is preferred for maintaining efficiencies with drivers less used to electric drive, particularly in city-center conditions. It involves repetitive on–off switching of the battery to the motor circuit. The chapter discusses the development history of electric vehicles (EV). A major problem with HEVs is their cost, which is exacerbated by having two drive systems in one vehicle. But the automotive industry has found a solution, micro-turbines together with their associated generators and accessories can be produced cheaply, mainly because they have a very low component count. These turbines are capable of operating on a wide variety of fuels and are considered to produce a very low level of pollutants.

An energy storage device

Abstract: An energy storage device (1) includes a cylindrical shrink wrap housing (2) having two opposed metal terminals (3, 4). An electrochemical device in the form of a dry cell alkaline battery (5) is disposed within housing (2) for providing an electrical potential between the terminals. An electric double layer supercapacitor (6) is wrapped around and mounted to housing (2) and connected to terminals (3, 4) in parallel with battery (5).

Lightning energy conversion using lasers

Abstract: Potential energy sources are being investigated for the socioeconomic needs and increased power demand. Systems employing nuclear, thermal, hydro, solar, volcano, MHD, tidal and wind power generation techniques already exist. This work describes our attempt to utilize the off-planet lightning charge to store super electrolytic batteries or super capacitors. The electrostatic charge on clouds can be shifted to earth through a conducive air plasma channel created by appropriate high power Q-switched and mode-locked laser. The pulsed laser may create a conducting path consisting of ionized air particles from earth to some upper atmosphere. An antenna connected to anode of super cell or positive terminal of the super capacitor will accumulate and store this charge for future use. The anode of battery or positive terminal of capacitor may be connected to earth to complete the circuit. Due to extremely loud thundering and tropical weather severity a detailed work was done on lightning regarding its temporal and spatial profiles to develop a reasonable model to explore transient charging characteristics. Experimental work in respect of laser inducted plasma wire creation and charging capabilities of super storage batteries or super capacitors is optimized. Latest experimental results are reported.