Showing papers on "Capacitance published in 2013"
Book•
14 Feb 2013
TL;DR: In this paper, the double-layer and surface functionalities at Carbon were investigated and the double layer at Capacitor Electrode Interfaces: its structure and Capacitance.
Abstract: 1 Introduction and Historical Perspective 2 Similarities and Differences between Supercapacitors and Batteries for Electrical Energy Storage 3 Energetics and Elements of Kinetics of Electrode Processes 4 Elements of Electrostatics Involved in Treatment of Double-Layers and Ions at Capacitors Electrode Interfaces 5 Behavior of Dielectrics in Capacitors and Theories of Dielectric Polarization 6 The Double-Layer at Capacitor Electrode Interfaces: Its Structure and Capacitance 7 Theoretical Treatment and Modeling of the Double-Layer at Electrode Interfaces 8 Behavior of the Double-Layer in Non-Aqueous Electrolytes and Non-Aqueous Electrolyte Capacitors 9 The Double-Layer and Surface Functionalities at Carbon 10 Electrochemical Capacitors Based on Pseudocapacitance 11 The Electrochemical Behavior of Ruthenium Oxide (RuO2) as a Material for Electrochemical Capacitors 12 Capacitance Behavior of Films Conducting, Electrochemically Reactive Polymers 13 The Electrolyte Factor in Supercapacitor Design and Performance: Conductivity, Ion-Pairing and Solvation 14 Electrochemical Behavior at Porous Electrodes Applications to Capacitors 15 Energy-Density and Power-Density of Electrical Energy Storage Devices 16 AC Impedance Behavior of Electrochemical Capacitors and Other Electrochemical Systems 17 Treatments of Impedance Behavior of Various Circuits and Modeling of Double-Layer Capacitor Frequency Response 18 Self-Discharge of Electrochemical Capacitors in Relation to that of at Batteries 19 Technology Development 20 Patent Survey
4,908 citations
TL;DR: This research might provide a method for flexible, lightweight, high-performance, low-cost, and environmentally friendly materials used in energy conversion and storage systems for the effective use of renewable energy.
Abstract: A lightweight, flexible, and highly efficient energy management strategy is needed for flexible energy-storage devices to meet a rapidly growing demand. Graphene-based flexible supercapacitors are one of the most promising candidates because of their intriguing features. In this report, we describe the use of freestanding, lightweight (0.75 mg/cm2), ultrathin (<200 μm), highly conductive (55 S/cm), and flexible three-dimensional (3D) graphene networks, loaded with MnO2 by electrodeposition, as the electrodes of a flexible supercapacitor. It was found that the 3D graphene networks showed an ideal supporter for active materials and permitted a large MnO2 mass loading of 9.8 mg/cm2 (∼92.9% of the mass of the entire electrode), leading to a high area capacitance of 1.42 F/cm2 at a scan rate of 2 mV/s. With a view to practical applications, we have further optimized the MnO2 content with respect to the entire electrode and achieved a maximum specific capacitance of 130 F/g. In addition, we have also explored t...
1,309 citations
TL;DR: A supercapacitor electrode composed of well-aligned CoO nanowire array grown on 3D nickel foam with polypyrrole (PPy) uniformly immobilized onto or firmly anchored to each nanowires surface to boost the pseudocapacitive performance.
Abstract: We have developed a supercapacitor electrode composed of well-aligned CoO nanowire array grown on 3D nickel foam with polypyrrole (PPy) uniformly immobilized onto or firmly anchored to each nanowire surface to boost the pseudocapacitive performance. The electrode architecture takes advantage of the high electrochemical activity from both the CoO and PPy, the high electronic conductivity of PPy, and the short ion diffusion pathway in ordered mesoporous nanowires. These merits together with the elegant synergy between CoO and PPy lead to a high specific capacitance of 2223 F g–1 approaching the theoretical value, good rate capability, and cycling stability (99.8% capacitance retention after 2000 cycles). An aqueous asymmetric supercapacitor device with a maximum voltage of 1.8 V fabricated by using our hybrid array as the positive electrode and activated carbon film as the negative electrode has demonstrated high energy density (∼43.5 Wh kg–1), high power density (∼5500 W kg–1 at 11.8 Wh kg–1) and outstandi...
1,220 citations
TL;DR: The integrated electrochemical performance of the amorphous nickel hydroxide is commensurate with crystalline materials in supercapacitors, and these findings promote the application ofAmorphous nanostructures as advanced electrochemical pseudocapacitor materials.
Abstract: Nickel hydroxide is a promising material for capacitor electrodes and most research has focussed on the crystalline form. Here, the authors report that amorphous nickel hydroxide nanospheres, which may be synthesized relatively easily, also exhibit excellent integrated electrochemical performance.
1,083 citations
TL;DR: These exquisite carbons were able to be achieved by simple hydrothermal carbonization combined with activation by taking advantage of the complex multilayered structure of a hemp bast fiber precursor, providing among the best power-energy characteristics ever reported for an electrochemical capacitor.
Abstract: We created unique interconnected partially graphitic carbon nanosheets (10–30 nm in thickness) with high specific surface area (up to 2287 m2 g–1), significant volume fraction of mesoporosity (up to 58%), and good electrical conductivity (211–226 S m–1) from hemp bast fiber. The nanosheets are ideally suited for low (down to 0 °C) through high (100 °C) temperature ionic-liquid-based supercapacitor applications: At 0 °C and a current density of 10 A g–1, the electrode maintains a remarkable capacitance of 106 F g–1. At 20, 60, and 100 °C and an extreme current density of 100 A g–1, there is excellent capacitance retention (72–92%) with the specific capacitances being 113, 144, and 142 F g–1, respectively. These characteristics favorably place the materials on a Ragone chart providing among the best power–energy characteristics (on an active mass normalized basis) ever reported for an electrochemical capacitor: At a very high power density of 20 kW kg–1 and 20, 60, and 100 °C, the energy densities are 19, 3...
826 citations
TL;DR: A 3D highly conductive urchin-like NiCo₂S₄ nanostructure has been successfully prepared using a facile precursor transformation method and demonstrates superior electrochemical performance with ultrahigh high-rate capacitance, very high specific capacitance and excellent cycling stability.
Abstract: A 3D highly conductive urchin-like NiCo2S4 nanostructure has been successfully prepared using a facile precursor transformation method. Remarkably, the NiCo2S4 electroactive material demonstrates superior electrochemical performance with ultrahigh high-rate capacitance, very high specific capacitance, and excellent cycling stability.
817 citations
TL;DR: A fingerprint of the charge accumulation in high density of states of the perovskite absorber material has been observed at the capacitance of the samples, indicating that it constitutes a new kind of photovoltaic device, differentiated from sensitized solar cells, which will require its own methods of study, characterization and optimization.
Abstract: Photovoltaic conversion requires two successive steps: accumulation of a photogenerated charge and charge separation. Determination of how and where charge accumulation is attained and how this accumulation can be identified is mandatory for understanding the performance of a photovoltaic device and for its further optimization. Here we analyse the mechanism of carrier accumulation in lead halide perovskite, CH3NH3PbI3, thin-absorber solar cells by means of impedance spectroscopy. A fingerprint of the charge accumulation in high density of states of the perovskite absorber material has been observed at the capacitance of the samples. This is, as far as we know, the first observation of charge accumulation in light-absorbing material for nanostructured solar cells, indicating that it constitutes a new kind of photovoltaic device, differentiated from sensitized solar cells, which will require its own methods of study, characterization and optimization.
761 citations
TL;DR: Inspired by the results that the electrochemical activity and electrical conductivity of ZnO nanowires were greatly improved after hydrogenation, hydrogenated single-crystal ZnNO@amorphous ZNO-doped MnO2 core-shell nanocables (HZM) on carbon cloth as SC electrodes were designed and fabricated, showing excellent performance.
Abstract: Although MnO2 is a promising material for supercapacitors (SCs) due to its excellent electrochemical performance and natural abundance, its wide application is limited by poor electrical conductivity. Inspired by our results that the electrochemical activity and electrical conductivity of ZnO nanowires were greatly improved after hydrogenation, we designed and fabricated hydrogenated single-crystal ZnO@amorphous ZnO-doped MnO2 core–shell nanocables (HZM) on carbon cloth as SC electrodes, showing excellent performance such as areal capacitance of 138.7 mF/cm2 and specific capacitance of 1260.9 F/g. Highly flexible all-solid-state SCs were subsequently assembled with these novel HZM electrodes using polyvinyl alcohol/LiCl electrolyte. The working devices achieved very high total areal capacitance of 26 mF/cm2 and retained 87.5% of the original capacitance even after 10 000 charge/discharge cycles. An integrated power pack incorporating series-wound SCs and dye-sensitized solar cells was demonstrated for sta...
748 citations
TL;DR: This work constitutes the first demonstration of using VN nanowires as high energy anode, which could potentially improve the performance of energy storage devices.
Abstract: To push the energy density limit of asymmetric supercapacitors (ASCs), a new class of anode materials is needed. Vanadium nitride (VN) holds great promise as anode material for ASCs due to its large specific capacitance, high electrical conductivity, and wide operation windows in negative potential. However, its poor electrochemical stability severely limits its application in SCs. In this work, we demonstrated high energy density, stable, quasi-solid-state ASC device based on porous VN nanowire anode and VOx nanowire cathode for the first time. The VOx//VN-ASC device exhibited a stable electrochemical window of 1.8 V and excellent cycling stability with only 12.5% decrease of capacitance after 10 000 cycles. More importantly, the VOx//VN-ASC device achieved a high energy density of 0.61 mWh cm–3 at current density of 0.5 mA cm–2 and a high power density of 0.85 W cm–3 at current density of 5 mA cm–2. These values are substantially enhanced compared to most of the reported quasi/all-solid-state SC devices...
665 citations
TL;DR: In this paper, a self-assembled reduced graphene oxide (RGO)/MnO2/GrMoO(2) composite was used as a positive electrode and a RGO/MoO3 composite as a negative electrode in safe aqueous Na2SO4 electrolyte.
Abstract: Asymmetric supercapacitors with high energy density are fabricated using a self-assembled reduced graphene oxide (RGO)/MnO2 (GrMnO(2)) composite as a positive electrode and a RGO/MoO3 (GrMoO(3)) composite as a negative electrode in safe aqueous Na2SO4 electrolyte. The operation voltage is maximized by choosing two metal oxides with the largest work function difference. Because of the synergistic effects of highly conductive graphene and highly pseudocapacitive metal oxides, the hybrid nanostructure electrodes exhibit better charge transport and cycling stability. The operation voltage is expanded to 2.0 V in spite of the use of aqueous electrolyte, revealing a high energy density of 42.6 Wh kg(-1) at a power density of 276 W kg(-1) and a maximum specific capacitance of 307 F g(-1), consequently giving rise to an excellent Ragone plot. In addition, the GrMnO(2)//GrMoO(3) supercapacitor exhibits improved capacitance with cycling up to 1000 cycles, which is explained by the development of micropore structures during the repetition of ion transfer. This strategy for the choice of metal oxides provides a promising route for next-generation supercapacitors with high energy and high power densities.
597 citations
TL;DR: In this paper, the Ni3S2@Ni(OH)2/3DGN was synthesized using a one-step hydrothermal reaction, and the morphological and structural evolution of the 3DGN has been investigated.
Abstract: A three-dimensional graphene network (3DGN) grown on nickel foam is an excellent template for the synthesis of graphene-based composite electrodes for use in supercapacitors. Ni(OH)2nanosheets coated onto single-crystal Ni3S2nanorods grown on the surface of the 3DGN (referred to as the Ni3S2@Ni(OH)2/3DGN) are synthesized using a one-step hydrothermal reaction. SEM, TEM, XRD and Raman spectroscopy are used to investigate the morphological and structural evolution of the Ni3S2@Ni(OH)2/3DGN. Detailed electrochemical characterization shows that the Ni3S2@Ni(OH)2/3DGN exhibits high specific capacitance (1277 F g−1 at 2 mV s−1 and 1037.5 F g−1 at 5.1 A g−1) and areal capacitance (4.7 F cm−2 at 2 mV s−1 and 3.85 F cm−2 at 19.1 mA cm−2) with good cycling performance (99.1% capacitance retention after 2000 cycles).
TL;DR: A new approach to large-scale fabrication of high-capacitance, two-dimensional MoS2 film-based micro-supercapacitors is demonstrated via simple and low-cost spray painting of MoS 2 nanosheets on Si/SiO2 chip and subsequent laser patterning.
Abstract: Micrometer-sized electrochemical capacitors have recently attracted attention due to their possible applications in micro-electronic devices. Here, a new approach to large-scale fabrication of high-capacitance, two-dimensional MoS2 film-based micro-supercapacitors is demonstrated via simple and low-cost spray painting of MoS2 nanosheets on Si/SiO2 chip and subsequent laser patterning. The obtained micro-supercapacitors are well defined by ten interdigitated electrodes (five electrodes per polarity) with 4.5 mm length, 820 μm wide for each electrode, 200 μm spacing between two electrodes and the thickness of electrode is ∼0.45 μm. The optimum MoS2 -based micro-supercapacitor exhibits excellent electrochemical performance for energy storage with aqueous electrolytes, with a high area capacitance of 8 mF cm(-2) (volumetric capacitance of 178 F cm(-3) ) and excellent cyclic performance, superior to reported graphene-based micro-supercapacitors. This strategy could provide a good opportunity to develop various micro-/nanosized energy storage devices to satisfy the requirements of portable, flexible, and transparent micro-electronic devices.
TL;DR: A flexible and weaveable electric double-layer capacitor wire is developed by twisting two aligned carbon nanotube/ordered mesoporous carbon composite fibers with remarkable mechanical and electronic properties as electrodes that are particularly promising for portable and wearable electronic devices.
Abstract: A flexible and weaveable electric double-layer capacitor wire is developed by twisting two aligned carbon nanotube/ordered mesoporous carbon composite fibers with remarkable mechanical and electronic properties as electrodes. This capacitor wire exhibits high specific capacitance and long life stability. Compared with the conventional planar structure, the capacitor wire is also lightweight and can be integrated into various textile structures that are particularly promising for portable and wearable electronic devices.
TL;DR: Because of the unique microstructure with combination of two layered materials, WS2/RGO hybrids emerge as a promising supercapacitor electrode material with high specific capacitance, energy density, and excellent cycling stability.
Abstract: We report here the synthesis of layer structured WS2/reduced graphene oxide (RGO) hybrids by a facile hydrothermal method for its possible application as supercapacitor materials in energy storage devices. The prepared two-dimensional materials are characterized thoroughly by various analytical techniques to ascertain their structure and to confirm the absence of any impurities. Two-electrode capacitance measurements have been carried out in aqueous 1 M Na2SO4. The WS2/RGO hybrids exhibited enhanced supercapacitor performance with specific capacitance of 350 F/g at a scan rate of 2 mV/s. The obtained capacitance values of WS2/RGO hybrids are about 5 and 2.5 times higher than bare WS2 and RGO sheets. Because of the unique microstructure with combination of two layered materials, WS2/RGO hybrids emerge as a promising supercapacitor electrode material with high specific capacitance, energy density, and excellent cycling stability.
TL;DR: In this article, a 3D molybdenum disulfide (MoS 2 )-graphene composite is synthesized by a modified l -cysteine-assisted solution-phase method.
TL;DR: This work confirms that the as-prepared architectures can not only be applied in high energy density fields, but also be used in high power density applications, such as electric vehicles, flexible electronics, and energy storage devices.
Abstract: Hierarchical ZnCo2O4/nickel foam architectures were first fabricated from a simple scalable solution approach, exhibiting outstanding electrochemical performance in supercapacitors with high specific capacitance (∼1400 F g–1 at 1 A g–1), excellent rate capability (72.5% capacity retention at 20 A g–1), and good cycling stability (only 3% loss after 1000 cycles at 6 A g–1). All-solid-state supercapacitors were also fabricated by assembling two pieces of the ZnCo2O4-based electrodes, showing superior performance in terms of high specific capacitance and long cycling stability. Our work confirms that the as-prepared architectures can not only be applied in high energy density fields, but also be used in high power density applications, such as electric vehicles, flexible electronics, and energy storage devices.
TL;DR: In this article, the activated carbons (ACs) were characterized by XRD, Raman, FT-IR and surface area, pore size and pore volume analysis.
Abstract: Halogen (iodide, I−) added aqueous electrolyte facilitates the capacitive behaviour of biomass derived activated carbon based electric double layer capacitors. To produce economically viable electrodes in large scale for supercapacitors (SCs), the activated carbons (ACs) prepared from Eichhornia crassipes (common water hyacinth) by ZnCl2 activation. The prepared ACs were characterized by XRD, Raman, FT-IR and surface area, pore size and pore volume analysis. The electrochemical properties of the SCs were studied using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), electrochemical impedance spectroscopy (EIS) and cycling stability. The 3I−/I3−, 2I−/ I2, 2I3−/3I2 and I2/IO3− pairs produce redox peaks in CV and a large Faradaic plateau in charge–discharge curves. Similarly, I− ions improves the good ionic conductivity (lower charge transfer resistance) at the electrode/electrolyte interface which was identified through EIS studies. The calculated specific capacitance and energy density was 472 F g−1 and 9.5 W h kg−1 in aqueous solution of 1 M H2SO4. Interestingly, nearly two-fold improved specific capacitance and energy density of 912 F g−1 and 19.04 W h kg−1 were achieved when 0.08 M KI was added in 1 M H2SO4 electrolyte with excellent cycle stability over 4000 cycles. Subsequently, this improved specific capacitance and energy density was compared with 0.08 M KBr added to 1 M H2SO4 (572 F g−1, 11.6 W h kg−1) and 0.08 M KI added to 1 M Na2SO4 (604 F g−1, 12.3 W h kg−1) as electrolytes.
TL;DR: In this article, a simple and low-cost method involving pencil-drawing and electrodeposition is introduced to fabricate graphite/polyaniline hybrid electrodes on paper for flexible solid-state supercapacitors.
Journal Article•
TL;DR: In this article, the authors presented a work on capacitance characterization of organic photovoltaic cells and rectified a mistake which appeared in Carr and Chaudhary's work.
Abstract: In the 100th volume of Applied Physics Letters Carr and Chaudhary have presented a work on capacitance characterization of organic photovoltaic cells. The work concerns small signal measurements of various organic photovoltaic structures. The authors however limit their considerations to one part of small signal response, namely to capacitance measured either in parallel mode or in series mode. This attitude generally does not lead to accurate capacitance in organic devices and only for certain cases can result in appropriate values. Moreover, confusing C’’ with C’ they classify our work into “improper” models. In this comments, we go into details of capacitance characterization of organic photovoltaic cells and we rectify a mistake which appear in Carr and Chaudhary’s work.
TL;DR: 3D N-doped graphene-CNT networks can be obtained by hydrothermal treatment, freeze-drying and subsequent carbonization of graphene oxide-dispersed pristine CNTs in the presence of pyrrole and show high specific capacitance, good rate capability and still retain ∼96% of the initial capacitance even after 3000 cycles.
TL;DR: This review describes recent developments in the field-effect transistors (FETs) with gate dielectrics of ionic liquids, which have attracted much attention due to their wide electrochemical windows, low vapor pressures, and high chemical and physical stability.
Abstract: Charge carrier control is a key issue in the development of electronic functions of semiconductive materials. Beyond the simple enhancement of conductivity, high charge carrier accumulation can realize various phenomena, such as chemical reaction, phase transition, magnetic ordering, and superconductivity. Electric double layers (EDLs), formed at solid-electrolyte interfaces, induce extremely large electric fields. This results in a high charge carrier accumulation in the solid, much more effectively than solid dielectric materials. In the present review, we describe recent developments in the field-effect transistors (FETs) with gate dielectrics of ionic liquids, which have attracted much attention due to their wide electrochemical windows, low vapor pressures, and high chemical and physical stability. We explain the capacitance effects of ionic liquids, and describe the various combinations of ionic liquids and organic and inorganic semiconductors that are used to achieve such effects as high transistor performance, insulator-metal transitions, superconductivity, and ferromagnetism, in addition to the applications of the ionic-liquid EDL-FETs in logic devices. We discuss the factors controlling the mobility and threshold voltage in these types of FETs, and show the ionic liquid dependence of the transistor performance.
17 Mar 2013
TL;DR: In this paper, the operation of a battery charging system, which is comprised of one Full Bridge (FB) AC-DC stage and one Dual Active Bridge (DAB) DCDC stage, with charging current containing low frequency ripple at two times line frequency, designated as sinusoidal charging is investigated.
Abstract: High power density is strongly preferable for the on-board battery charger of Plug-in Hybrid Electric Vehicle (PHEV). Wide band gap devices, such as Gallium Nitride HEMTs are being explored to push to higher switching frequency and reduce passive component size. In this case, the bulk DC link capacitor of AC-DC Power Factor Correction (PFC) stage, which is usually necessary to store ripple power of two times the line frequency in a DC current charging system, becomes a major barrier on power density. If low frequency ripple is allowed in the battery, the DC link capacitance can be significantly reduced. This paper focuses on the operation of a battery charging system, which is comprised of one Full Bridge (FB) AC-DC stage and one Dual Active Bridge (DAB) DC-DC stage, with charging current containing low frequency ripple at two times line frequency, designated as sinusoidal charging. DAB operation under sinusoidal charging is investigated. Two types of control schemes are proposed and implemented in an experimental prototype. It is proved that closed loop current control is the better. Full system test including both FB AC-DC stage and DAB DC-DC stage verified the concept of sinusoidal charging, which may lead to potentially very high power density battery charger for PHEV.
TL;DR: In this paper, a CNF-RGO hybrid aerogel-based flexible supercapacitor was proposed for flexible super-capacitors with high capacitance (207 F g−1).
Abstract: Cellulose nanofibers are selected as nano-spacers, electrolyte nano-reservoirs and hierarchical nanostructure makers of CNF–RGO hybrid aerogel. The CNF–RGO hybrid aerogel based flexible supercapacitor exhibits high capacitance (207 F g−1). Taking its higher capacitance, low cost and environmentally friendly nature, they have great potential for use in flexible supercapacitors.
TL;DR: In this paper, the authors introduced a new concept to fabricate on chip, all solid-state and flexible micro-supercapacitors based on MnOx/Au multilayers, which are compatible with current microelectronics.
Abstract: In this work, we introduce a new concept to fabricate on chip, all solid-state and flexible micro-supercapacitors based on MnOx/Au multilayers, which are compatible with current microelectronics. The micro-supercapacitor exhibits a maximum energy density of 1.75 mW h cm−3 and a maximum power density of 3.44 W cm−3, which are both much higher than the values obtained for other solid-state supercapacitors. At a scan rate of 1 V s−1, a volumetric capacitance of 32.8 F cm−3 is obtained for MnOx/Au multilayer electrodes, which is much higher than the bare MnOx electrode. Electrochemical impedance spectroscopy (EIS) and evolution complex capacitance confirm that the electrical conductivity of MnOx is improved due to the incorporation of gold, and a low relaxation time constant around 5 ms is observed. The MnOx/Au multilayer micro-supercapacitor also shows good long-term cycling stability, with a capacitance retention rate of 74.1% after a large cycling number of 15000 times. Compared with other supercapacitors, which are not portable and are relatively bulky, the device demonstrated here allows fast and reliable applications in a portable and smart fashion. Furthermore, the nature of the process allows the micro-supercapacitor to be integrated with other micro-devices, to meet the need for micro-scale energy storage.
TL;DR: This study reports a simple synthesis of amorphous nickel tungstate (NiWO4) nanostructure and its application as a novel cathode material for supercapacitors and results demonstrate that the material synthesized at 70 °C has shown the highest specific capacitance.
Abstract: This study reports a simple synthesis of amorphous nickel tungstate (NiWO4) nanostructure and its application as a novel cathode material for supercapacitors. The effect of reaction temperature on the electrochemical properties of the NiWO4 electrode was studied, and results demonstrate that the material synthesized at 70 °C (NiW-70) has shown the highest specific capacitance of 586.2 F g(-1) at 0.5 A g(-1) in a three-electrode system. To achieve a high energy density, a NiW-70//activated carbon asymmetric supercapacitor is successfully assembled by use of NiW-70 and activated carbon as the cathode and anode, respectively, and then, its electrochemical performance is characterized by cyclic voltammetry and galvanostatic charge-discharge measurements. The results show that the assembled asymmetric supercapacitor can be cycled reversibly between 0 and 1.6 V with a high specific capacitance of 71.1 F g(-1) at 0.25 A g(-1), which can deliver a maximum energy density of 25.3 Wh kg(-1) at a power density of 200 W kg(-1). Furthermore, this asymmetric supercapacitor also presented an excellent, long cycle life along with 91.4% specific capacitance being retained after 5000 consecutive times of cycling.
TL;DR: In this paper, a sacrificial template method based on the Kirkendall effect was used to synthesize NiCo2S4 porous nanotubes, which showed a specific capacitance of 1093 F g−1 at a current density of 0.2 A g− 1.
Abstract: NiCo2S4 porous nanotubes are synthesised by a sacrificial template method based on the Kirkendall effect. The as-prepared NiCo2S4 nanotube electrode shows a specific capacitance of 1093 F g−1 at a current density of 0.2 A g−1 (933 F g−1 at 1 A g−1).
TL;DR: A solid-state flexible supercapacitor based on organic-inorganic composite structure was fabricated through an “in situ growth for conductive wrapping” method and an electrode material of polypyrrole-MnO2 nanoflakes-carbon fiber hybrid structure was obtained.
Abstract: A solid-state flexible supercapacitor (SC) based on organic-inorganic composite structure was fabricated through an “in situ growth for conductive wrapping” and an electrode material of polypyrrole (PPy)-MnO2 nanoflakes-carbon fiber (CF) hybrid structure was obtained. The conductive organic material of PPy greatly improved the electrochemical performance of the device. With a high specific capacitance of 69.3 F cm−3 at a discharge current density of 0.1 A cm−3 and an energy density of 6.16 × 10−3 Wh cm−3 at a power density of 0.04 W cm−3, the device can drive a commercial liquid crystal display (LCD) after being charged. The organic-inorganic composite active materials have enormous potential in energy management and the “in situ growth for conductive wrapping” method might be generalized to open up new strategies for designing next-generation energy storage devices.
TL;DR: A general model using the slit/cylindrical NL-DFT approach is proposed for the estimation of the specific capacitance of sp(2) carbon materials, which offers a simple but reliable method to predict the capacitance performance of these materials, thus speeding up the design and screening of the materials for high-performance supercapacitor and other surface area related devices.
Abstract: A series of sp2 carbon materials with different specific surface area (SSA) and controlled pore size distribution (PSD) were synthesized at large scale through a facile and low-cost method. The SSA and PSD of these carbon materials were controlled by using different carbon sources and preparation methods. With different total and effective SSA (E-SSA) and PSD, the impacts on their capacitance performance were investigated thoroughly, which demonstrated that both E-SSA and PSD played the most important roles in their capacitance performance. Furthermore, theoretical modeling was performed, and the results are in agreement with the experimental results for the influence of E-SSA and PSD on their capacitance performance. Based on these, a general model using the slit/cylindrical NL-DFT approach is proposed for the estimation of the specific capacitance of sp2 carbon materials, which offers a simple but reliable method to predict the capacitance performance of these materials, thus speeding up the design and ...
TL;DR: In this article, the state-of-the-art on EDL capacitors is presented, with the objective to better understand their operating principles and to improve their performance, in particular for carbons having subnanometric pores where ions of the electrolyte are distorted and partly desolvated.
TL;DR: A fibre-shaped solid electrochemical capacitor based on electrochemically reduced graphene oxide has been fabricated, exhibiting high specific capacitance and rate capability, long cycling life and attractive flexibility.