Showing papers on "Supercapacitor published in 2009"
TL;DR: It is shown that batteries which obtain high energy density by storing charge in the bulk of a material can also achieve ultrahigh discharge rates, comparable to those of supercapacitors.
Abstract: The storage of electrical energy at high charge and discharge rate is an important technology in today's society, and can enable hybrid and plug-in hybrid electric vehicles and provide back-up for wind and solar energy. It is typically believed that in electrochemical systems very high power rates can only be achieved with supercapacitors, which trade high power for low energy density as they only store energy by surface adsorption reactions of charged species on an electrode material. Here we show that batteries which obtain high energy density by storing charge in the bulk of a material can also achieve ultrahigh discharge rates, comparable to those of supercapacitors. We realize this in LiFePO(4) (ref. 6), a material with high lithium bulk mobility, by creating a fast ion-conducting surface phase through controlled off-stoichiometry. A rate capability equivalent to full battery discharge in 10-20 s can be achieved.
3,187 citations
TL;DR: In this paper, a supercapacitor with a maximum specific capacitance of 205 F/g with a measured power density of 10 kW/kg at energy density of 28.5 Wh/kg in an aqueous electrolyte solution has been obtained.
Abstract: Graphene materials (GMs) as supercapacitor electrode materials have been investigated. GMs are prepared from graphene oxide sheets, and subsequently suffer a gas-based hydrazine reduction to restore the conducting carbon network. A maximum specific capacitance of 205 F/g with a measured power density of 10 kW/kg at energy density of 28.5 Wh/kg in an aqueous electrolyte solution has been obtained. Meanwhile, the supercapacitor devices exhibit excellent long cycle life along with ∼90% specific capacitance retained after 1200 cycle tests. These remarkable results demonstrate the exciting commercial potential for high performance, environmentally friendly and low-cost electrical energy storage devices based on this new 2D graphene material.
2,308 citations
TL;DR: This graphene-based composite paper electrode, consisting of graphene/polyaniline composite sheets as building blocks, shows a favorable tensile strength and a stable large electrochemical capacitance, which outperforms many other currently available carbon-based flexible electrodes and is hence particularly promising for flexible supercapacitors.
Abstract: Freestanding and flexible graphene/polyaniline composite paper was prepared by an in situ anodic electropolymerization of polyaniline film on graphene paper. This graphene-based composite paper electrode, consisting of graphene/polyaniline composite sheets as building blocks, shows a favorable tensile strength of 12.6 MPa and a stable large electrochemical capacitance (233 F g(-1) and 135 F cm(-3) for gravimetric and volumetric capacitances), which outperforms many other currently available carbon-based flexible electrodes and is hence particularly promising for flexible supercapacitors.
1,447 citations
TL;DR: Using a printable aqueous gel electrolyte as well as an organic liquid electrolyte, the performances of the devices show very high energy and power densities which is comparable to performance in other SWCNT-based supercapacitor devices fabricated using different methods.
Abstract: Thin film supercapacitors were fabricated using printable materials to make flexible devices on plastic. The active electrodes were made from sprayed networks of single-walled carbon nanotubes (SWCNTs) serving as both electrodes and charge collectors. Using a printable aqueous gel electrolyte as well as an organic liquid electrolyte, the performances of the devices show very high energy and power densities (6 W h/kg for both electrolytes and 23 and 70 kW/kg for aqueous gel electrolyte and organic electrolyte, respectively) which is comparable to performance in other SWCNT-based supercapacitor devices fabricated using different methods. The results underline the potential of printable thin film supercapacitors. The simplified architecture and the sole use of printable materials may lead to a new class of entirely printable charge storage devices allowing for full integration with the emerging field of printed electronics.
1,444 citations
TL;DR: It is suggested that this conductive paper can be a highly scalable and low-cost solution for high-performance energy storage devices and as an excellent lightweight current collector in lithium-ion batteries to replace the existing metallic counterparts.
Abstract: Paper, invented more than 2,000 years ago and widely used today in our everyday lives, is explored in this study as a platform for energy-storage devices by integration with 1D nanomaterials. Here, we show that commercially available paper can be made highly conductive with a sheet resistance as low as 1 ohm per square (Ω/sq) by using simple solution processes to achieve conformal coating of single-walled carbon nanotube (CNT) and silver nanowire films. Compared with plastics, paper substrates can dramatically improve film adhesion, greatly simplify the coating process, and significantly lower the cost. Supercapacitors based on CNT-conductive paper show excellent performance. When only CNT mass is considered, a specific capacitance of 200 F/g, a specific energy of 30–47 Watt-hour/kilogram (Wh/kg), a specific power of 200,000 W/kg, and a stable cycling life over 40,000 cycles are achieved. These values are much better than those of devices on other flat substrates, such as plastics. Even in a case in which the weight of all of the dead components is considered, a specific energy of 7.5 Wh/kg is achieved. In addition, this conductive paper can be used as an excellent lightweight current collector in lithium-ion batteries to replace the existing metallic counterparts. This work suggests that our conductive paper can be a highly scalable and low-cost solution for high-performance energy storage devices.
1,188 citations
TL;DR: In this article, a novel high performance electrode material based on fibrillar polyaniline (PANI) doped with graphene oxide sheets was synthesized via in situ polymerization of monomer in the presence of graphene oxide, with a high conductivity of 10 S cm −1 at 22°C for the obtained nanocomposite with a mass ratio of aniline/graphite oxide, 100:1.
753 citations
TL;DR: In this paper, the performance of MnO2 nanorods prepared by a precipitation reaction was investigated in 0.5 mol/L Li2SO4, Na2SO 4, and KSO4 aqueous electrolyte solutions.
Abstract: The electrochemical performance of MnO2 nanorods prepared by a precipitation reaction was investigated in 0.5 mol/L Li2SO4, Na2SO4, and K2SO4 aqueous electrolyte solutions. Results show that at the slow scan rates, the nanorods show the largest capacitance (201 F/g) in Li2SO4 electrolyte since the reversible intercalation/deintercalation of Li+ in the solid phase produces an additional capacitance besides the capacitance based on the absorption/desorption reaction. At fast scan rates they show the largest capacitance in the K2SO4 electrolyte due to the smallest hydration radius of K+, highest ionic conductivity, and lowest equivalent series resistance (ESR). An asymmetric activated carbon (AC)/K2SO4/MnO2 supercapacitor could be cycled reversibly between 0 and 1.8 V with an energy density of 17 Wh/kg at 2 kW/kg, much higher than those of the AC/K2SO4/AC supercapacitor and AC/Li2SO4/LiMn2O4 hybrid supercapacitor. Moreover, this supercapacitor exhibits excellent cycling behavior with no more than 6% capacita...
637 citations
TL;DR: In this paper, a general strategy has been demonstrated to achieve optimum electrochemical performance by constructing 3D nanocomposite architecture with the combination of nanosize Sn particles and graphene nanosheets.
Abstract: A general strategy has been demonstrated to achieve optimum electrochemical performance by constructing 3D nanocomposite architecture with the combination of nanosize Sn particles and graphene nanosheets. In the first step, the lithium storage properties of graphene have been investigated by first principles calculations. The results show that lithium can be stably stored on both sides of graphene sheets (LiC3), inducing in a theoretical capacity of 744 mAh/g. In the second step, a synthetic approach has been designed to prepare Sn/graphene nanocomposite with 3D architecture, in which Sn nanoparticles act as a spacer to effectively separate graphene nanosheets. FESEM and TEM analysis revealed the homogeneous distribution of Sn nanoparticles (2–5 nm) in graphene nanosheet matrix. Cyclic voltammetry measurement has proved the highly reversible nature of the reaction between Li+ and Sn/graphene nanocomposite. The 3D nanoarchitecture gives the Sn/graphene nanocomposite electrode an enhanced electrochemical performance. This strategy can be extended to prepare other anode and cathode materials for advanced energy storage and conversion devices such as lithium ion batteries, supercapacitors, and fuel cells.
563 citations
TL;DR: In this paper, a brief summary of recent research progress on carbon-based electrode materials for super-capacitors, as well as the importance of electrolytes in the development of supercapacitor technology is provided.
Abstract: This tutorial review provides a brief summary of recent research progress on carbon-based electrode materials for supercapacitors, as well as the importance of electrolytes in the development of supercapacitor technology. The basic principles of supercapacitors, the characteristics and performances of various nanostructured carbon-based electrode materials are discussed. Aqueous and non-aqueous electrolyte solutions used in supercapacitors are compared. The trend on future development of high-power and high-energy supercapacitors is analyzed.
541 citations
TL;DR: In this paper, the authors proposed a perfect energy source supplied by a polymer electrolyte membrane fuel cell (PEMFC) as a main power source and storage devices: battery and supercapacitor, for modern distributed generation system, particularly for future fuel cell vehicle applications.
523 citations
TL;DR: In this paper, the authors synthesize interpenetrating carbon nanotubes and vanadium pentoxide (V 2 O 5 ) nanowires networks via a simple in situ hydrothermal process.
Abstract: Nanocomposites of interpenetrating carbon nanotubes and vanadium pentoxide (V 2 O 5 ) nanowires networks are synthesized via a simple in situ hydrothermal process. These fibrous nanocomposites are hierarchically porous with high surface area and good electric conductivity, which makes them excellent material candidates for supercapacitors with high energy density and power density. Nanocomposites with a capacitance up to 440 and 200 F g -1 are achieved at current densities of 0.25 and 10 A g -1 , respectively. Asymmetric devices based on these nanocomposites and aqueous electrolyte exhibit an excellent charge/discharge capability, and high energy densities of 16 W h kg -1 at a power density of 75 W kg -1 and 5.5 W h kg -1 at a high power density of 3750 W kg -1 . This performance is a significant improvement over current electrochemical capacitors and is highly competetive with Ni-MH batteries. This work provides a new platform for high-density electrical-energy storage for electric vehicles and other applications.
TL;DR: In this article, an asymmetric supercapacitor with activated carbon (AC)-Fe3O4 nanoparticles was assembled and characterized in 6 M KOH aqueous electrolyte for the first time.
Abstract: In this study, activated carbon (AC)-Fe3O4 nanoparticles asymmetric supercapacitor cells have been assembled and characterized in 6 M KOH aqueous electrolyte for the first time. The nanostructure Fe3O4 was prepared by the microwave method. It only cost several minutes to prepare magnetite nanoparticles with average particle size of 35 nm. The electrochemical performances of the hybrid AC-Fe3O4 supercapacitor were tested by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge−discharge tests. The results show that the asymmetric supercapacitor has electrochemical capacitance performance within potential range 0−1.2 V. The supercapacitor delivered a specific capacitance of 37.9 F/g at a current density of 0.5 mA/cm2. The result of cyclic characteristic test showed that it also can keep 82% of initial capacity over 500 cycles.
TL;DR: The effect of temperature on the kinetics and the diffusion mechanism of the ions in a supercapacitor assembled with single-walled carbon nanotube (SWNT) film electrodes and an organic electrolyte were thoroughly investigated and showed excellent stability in capacitance with more than 80% efficiency.
Abstract: The effect of temperature on the kinetics and the diffusion mechanism of the ions in a supercapacitor assembled with single-walled carbon nanotube (SWNT) film electrodes and an organic electrolyte were thoroughly investigated. An improved room temperature performance of the supercapacitor was observed due to the combined effects of an increase in the conductivity of the SWNT films and surface modifications on the SWNT films by repeatedly heating and cooling the supercapacitor between the temperatures of 25 and 100 °C. Modified Randles equivalent circuit was employed to carry out an extensive analysis of the Nyquist spectra measured at different temperatures between 25 and 100 °C in order to understand the fundamentals of the capacitive and resistive variations in the supercapacitor. The experimental results and their thorough analysis will have significant impact not only on the fundamental understanding of the temperature-dependent electrode/electrolyte interfacial properties but also on supercapacitor d...
TL;DR: The use of atomic layer deposition is reported to be used to fabricate arrays of metal-insulator-metal nanocapacitors in anodic aluminium oxide nanopores that have a capacitance per unit planar area significantly exceeding previously reported values.
Abstract: Nanostructured devices have the potential to serve as the basis for next-generation energy systems that make use of densely packed interfaces and thin films 1 . One approach to making such devices is to build multilayer structures of large area inside the open volume of a nanostructured template. Here, we report the use of atomic layer deposition to fabricate arrays of metal–insulator–metal nanocapacitors in anodic aluminium oxide nanopores. These highly regular arrays have a capacitance per unit planar area of 10 m Fc m 22 for 1-mm-thick anodic aluminium oxide and 100 m Fc m 22 for 10-mm-thick anodic aluminium oxide, significantly exceeding previously reported values for metal–insulator–metal capacitors in porous templates 2–6 . It should be possible to scale devices fabricated with this approach to make viable energy storage systems that provide both high energy density and high power density. The nanocapacitor structures in this Letter are formed of metal electrodes separated by a dielectric film; therefore they behave in the same manner as conventional electrostatic capacitors, in which charge is stored on opposing electrode surfaces. A characteristic feature of electrostatic capacitors is high power. This is because charge can be moved rapidly, with speeds limited only by external circuit RCs. However, energy storage is limited because only surface charge is used. In contrast, conventional electrochemical supercapacitors store charge in electric double layers or in faradic reactions, permitting larger energy density storage on the electrode surfaces. Power density is limited in these devices because of the requirement for mass transport of ions and/or redox reactions 7 . The use of highly regular nanostructures promises both high energy and high power density. For the nanocapacitors described in this Letter, the nanostructure significantly enhances capacitance density. The nanocapacitors demonstrate the high power (up to � 1 � 10 6 Wk g 21 ) typical of electrostatic capacitors while achieving the much higher energy density (� 0.7 Wh kg 21 ) characteristic of electrochemical supercapacitors. As a result, electrostatic nanocapacitors are attractive for high-burst-power applications requiring the energy density of supercapacitors. To obtain energy devices that achieve dense packing of active interfaces and thin films, nanoporous structures are required that have internal surfaces on which highly uniform films can be reproducibly formed. We make use of the self-assembly of regular nanopore arrays available from anodic aluminium oxide (AAO) formation together with multilayer atomic layer deposition (ALD) to form highly controlled, self-aligned nanocapacitors. ALD has become the leading process used to achieve such coatings, yielding a high degree of thickness control and conformality in the most demanding nanostructures, with features that are either highly ordered 8–10 or are random porous networks 11–13 . Nanostructures fabricated with AAO and ALD show a high degree of uniformity across massive arrays, imparting the regularity that is a key factor in the viability of any technology 8 . Our fabrication strategy makes use of AAO nanopore templates in combination with metal–insulator–metal (MIM) structures deposited in the nanopores by ALD. The anodization process produces an ultrahigh density (� 1 � 10 10 cm 22 ) of hexagonally arranged, uniform, self-assembled nanopores in AAO film on Al tens of micrometres deep, which provides a good template for
TL;DR: In this article, an asymmetric supercapacitor based on activated carbon (AC) and NaMnO 2 as electrodes and aqueous Na 2 SO 4 solution as electrolyte was assembled.
TL;DR: In this article, a paper-like carbon nanotube/polyaniline (CNT/PANI) composite was proposed to transform a brittle polymer into flexible films.
TL;DR: It is concluded that not only should the energy storage devices of a FCHEV be sized by their power and energy requirements, but the battery lifetime should also be considered.
Abstract: Combining high-energy-density batteries and high-power-density ultracapacitors in fuel cell hybrid electric vehicles (FCHEVs) results in a high-performance, highly efficient, low-size, and light system. Often, the battery is rated with respect to its energy requirement to reduce its volume and mass. This does not prevent deep discharges of the battery, which are critical to the lifetime of the battery. In this paper, the ratings of the battery and ultracapacitors are investigated. Comparisons of the system volume, the system mass, and the lifetime of the battery due to the rating of the energy storage devices are presented. It is concluded that not only should the energy storage devices of a FCHEV be sized by their power and energy requirements, but the battery lifetime should also be considered. Two energy-management strategies, which sufficiently divide the load power between the fuel cell stack, the battery, and the ultracapacitors, are proposed. A charging strategy, which charges the energy-storage devices due to the conditions of the FCHEV, is also proposed. The analysis provides recommendations on the design of the battery and the ultracapacitor energy-storage systems for FCHEVs.
TL;DR: Graphene-ZnO composite film was synthesized for its potential application in supercapacitors as discussed by the authors, which exhibited an enhanced capacitive behavior with better reversible charging/discharging ability and higher capacitance values.
TL;DR: Experimental results in a laboratory authenticate that energy-storage devices can assist the FC to meet the vehicle power demand and help achieve better performance, as well as to substantiate the excellent control schemes during motor-drive cycles.
Abstract: This paper studies the impact of fuel-cell (FC) performance and control strategies on the benefits of hybridization. One of the main weak points of the FC is slow dynamics dominated by a temperature and fuel-delivery system (pumps, valves, and, in some cases, a hydrogen reformer). As a result, fast load demand will cause a high voltage drop in a short time, which is recognized as a fuel-starvation phenomenon. Therefore, to employ an FC in vehicle applications, the electrical system must have at least an auxiliary power source to improve system performance when electrical loads demand high energy in a short time. The possibilities of using a supercapacitor or a battery bank as an auxiliary source with an FC main source are presented in detail. The studies of two hybrid power systems for vehicle applications, i.e., FC/battery and FC/supercapacitor hybrid power sources, are explained. Experimental results with small-scale devices (a polymer electrolyte membrane FC of 500 W, 40 A, and 13 V; a lead-acid battery module of 33 Ah and 48 V; and a supercapacitor module of 292 F, 500 A, and 30 V) in a laboratory authenticate that energy-storage devices can assist the FC to meet the vehicle power demand and help achieve better performance, as well as to substantiate the excellent control schemes during motor-drive cycles.
TL;DR: In this article, an asymmetric supercapacitor activated carbon/0.5-mol/l K2SO4/V2O5·0.6H2O was successfully assembled, which could be cycled reversibly in the voltage region of 0.8-1.8
TL;DR: In this article, a scalable spray deposition technique has been adopted to the fabrication of a flexible nanostructured hybrid supercapacitor based on thin film multi-walled carbon nanotube (MWNT) cathodes and hematite (α-Fe2O3)/MWNT composite anodes.
Abstract: A scalable spray deposition technique has been adopted to the fabrication of a flexible nanostructured hybrid supercapacitor based on thin film multi-walled carbon nanotube (MWNT) cathodes and hematite (α-Fe2O3)/MWNT composite anodes. On the basis of the total weight of the binder-free MWNT and α-Fe2O3/MWNT thin film composite electrodes, the hybrid supercapacitor provided a very high specific energy density of 50 Wh kg−1 at a specific power density of 1000 W kg−1 over the potential range 0–2.8 V, which was an energy density 8 times that of identically prepared symmetric supercapacitors with MWNT only electrodes under the same conditions. The superior electrochemical performance of the hybrid supercapacitor arrangement can be attributed to the incorporation of MWNTs into the α-Fe2O3 anodes, which leads to a decrease of internal resistance and an improvement in both the ion diffusion behaviour and the integrity of the α-Fe2O3 containing films.
TL;DR: In this article, a review deals with recent progress in the fabrication, microstructure, and energy storage performance of different carbon nanotube arrays (CNTAs) electrodes and their composites in electrochemical capacitors and lithium-ion batteries.
Abstract: One of the greatest challenges for our society is to provide powerful electrochemical energy conversion and storage devices. Electrochemical capacitors and lithium-ion batteries are among the most promising candidates in terms of power- and energy-densities. The choice of electrode material is key to improving the performance of these energy conversion devices. Carbon nanotube arrays (CNTAs) and their composites show good capacity, excellent rate performance, and long cycle life when used as electrode materials because they present superior electronic conductivity, high surface area, developed porous structure, and robust properties. This review deals with recent progress in the fabrication, microstructure, and energy storage performance of different CNTA electrodes and their composites in electrochemical capacitors and lithium-ion batteries. In particular, representative examples of our CNTA-based electrodes are highlighted.
TL;DR: In this paper, an interesting effect of iodide ions has been observed for positive electrode operating in a narrow range of potential and giving extremely high capacitance values exceeding 1840 F/g.
TL;DR: In this paper, multi-walled carbon nanotube (MWCNT)/polyaniline (PANI) composite films were prepared by in-situ electrochemical polymerization of an aniline solution containing different MWCNT contents.
TL;DR: In this article, a supercapacitor with the features of optical transparency and mechanical flexibility has been fabricated using metal oxide nanowire/carbon nanotube heterogeneous film, and studies found that the power density can reach 7.48 kW/kg after galvanostatic measurements.
Abstract: In this paper, a supercapacitor with the features of optical transparency and mechanical flexibility has been fabricated using metal oxide nanowire/carbon nanotube heterogeneous film, and studies found that the power density can reach 7.48 kW/kg after galvanostatic measurements. In addition, to study the stability of flexible and transparent supercapacitor, the device was examined for a large number of cycles and showed a good retention of capacity (∼88%). This approach could work as the platform for future transparent and flexible nanoelectronics.
TL;DR: In this article, the self-discharge of an electrochemical capacitor is characterized by measuring the decline of open-circuit voltage of the electrochemical capacitance, and the mechanisms of selfdischarge, leakage current, and diffusion of ions at the electrode-electrolyte interfaces are modeled by an electrical equivalent circuit.
Abstract: The self-discharge of an electrochemical capacitor, also referred to as a supercapacitor, is an important factor in determining the duration of maintaining stored energy, especially in low-duty-cycle applications. The study of self-discharge is conducted as follows: first, the self-discharge is characterized by measuring the decline of open-circuit voltage of the electrochemical capacitor. Second, the mechanisms of self-discharge, leakage current, and diffusion of ions at the electrode-electrolyte interfaces are modeled by an electrical equivalent circuit. The equivalent circuit elements are experimentally determined according to the self-discharge time behavior. In addition, the dependence of the self-discharge parameters on both temperature and initial voltage across the electrochemical capacitor is described in detail.
TL;DR: In this article, single-crystal α-MnO2 nanotubes were synthesized by a facile hydrothermal method without the assistance of a template, a surfactant and heat treatment.
TL;DR: In this article, a carbon-carbon composite electrode material for supercapacitors is prepared by simple KOH activation of waste newspaper, and the amorphous nature and surface morphology of the carbon composite are investigated by X-ray diffraction (XRD), N 2 adsorption/desorption and scanning electron microscopy.
TL;DR: In this paper, the capacitance of carbon nanosheets was measured by cyclic voltammetry in a standard electrochemical three-electrode cell, which contains a platinum counter electrode and a standard mercury/mercurous sulfate reference electrode in 6 M H 2 SO 4 electrolyte.