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1.
The ability to achieve high areal capacitance for oxide-based supercapacitor electrodes with high active mass loadings is critical for practical applications. This paper reports the feasibility of the fabrication of Mn3O4-multiwalled carbon nanotube (MWCNT) composites by the new salting-out method, which allows direct particle transfer from an aqueous synthesis medium to a 2-propanol suspension for the fabrication of advanced Mn3O4-MWCNT electrodes for supercapacitors. The electrodes show enhanced capacitive performance at high active mass loading due to reduced particle agglomeration and enhanced mixing of the Mn3O4 particles and conductive MWCNT additives. The strategy is based on the multifunctional properties of octanohydroxamic acid, which is used as a capping and dispersing agent for Mn3O4 synthesis and an extractor for particle transfer to the electrode processing medium. Electrochemical studies show that high areal capacitance is achieved at low electrode resistance. The electrodes with an active mass of 40.1 mg cm−2 show a capacitance of 4.3 F cm−2 at a scan rate of 2 mV s−1. Electron microscopy studies reveal changes in electrode microstructure during charge-discharge cycling, which can explain the increase in capacitance. The salting-out method is promising for the development of advanced nanocomposites for energy storage in supercapacitors.  相似文献   

2.
Cathodes for supercapacitors with enhanced capacitive performance are prepared using MnO2 as a charge storage material and carbon nanotubes (CNT) as conductive additives. The enhanced capacitive properties are linked to the beneficial effects of catecholate molecules, such as chlorogenic acid and 3,4,5-trihydroxybenzamide, which are used as co-dispersants for MnO2 and CNT. The dispersant interactions with MnO2 and CNT are discussed in relation to the chemical structures of the dispersant molecules and their biomimetic adsorption mechanisms. The dispersant adsorption is a key factor for efficient co-dispersion in ethanol, which facilitated enhanced mixing of the nanostructured components and allowed for improved utilization of charge storage properties of the electrode materials with high active mass of 40 mg cm−2. Structural peculiarities of the dispersant molecules are discussed, which facilitate dispersion and charging. Capacitive properties are analyzed using cyclic voltammetry, chronopotentiometry and impedance spectroscopy. A capacitance of 6.5 F cm−2 is achieved at a low electrical resistance. The advanced capacitive properties of the electrodes are linked to the microstructures of the electrodes prepared in the presence of the dispersants.  相似文献   

3.
MnO2 nanowires were electrodeposited onto carbon nanotube (CNT) paper by a cyclic voltammetric technique. The as-prepared MnO2 nanowire/CNT composite paper (MNCCP) can be used as a flexible electrode for electrochemical supercapacitors. Electrochemical measurements showed that the MNCCP electrode displayed specific capacitances as high as 167.5 F g−1 at a current density of 77 mA g−1. After 3000 cycles, the composite paper can retain more than 88% of initial capacitance, showing good cyclability. The CNT paper in the composite acted as a good conductive and active substrate for flexible electrodes in supercapacitors, and the nanowire structure of the MnO2 could facilitate the contact of the electrolyte with the active materials, and thus increase the capacitance.  相似文献   

4.
Nanosized Fe3O4-modified activated carbon composites for supercapacitor electrodes have been investigated. Structural and morphological characterizations of activated materials are carried out using X-ray diffraction and scanning electron microscopy, respectively. The electrochemical performances of the composite electrodes are evaluated by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. The experimental results show that the specific capacitances of the 10 wt % Fe3O4-modified activated carbon composite electrode (154.3 F g?1) is highly improved compared with that of Fe3O4 (78.5 F g?1) and AC (79.2 F g?1) at the current density of 5 mA cm?2, respectively. The charge/discharge tests show that it could retain 79.6% of its initial capacitance over 1000 cycles, suggesting its potential application for the fabrication of high-quality supercapacitors.  相似文献   

5.
Aqueous supercapacitors based on neutral solutions have the advantages of high-ionic conductivity, being environmentally friendly, safe, and low cost. However, the operating potential window for most aqueous electrolytes is far lower than that of organic electrolytes that are commonly used in commercial supercapacitors. In this work, we report on the fabrication of a wide potential window, high-energy aqueous asymmetric supercapacitor, without sacrificing power, by using a nanostructured LiMn2O4/reduced graphene oxide (LMO–rGO) nanocomposite. We synthesized the uniformly distributed LMO in the LMO–rGO nanocomposite using a co-precipitation route followed by a low-temperature hydrothermal treatment. In a three-electrode cell setup, the specific capacitance of the LMO–rGO nanocomposite electrode at 1 A/g (1.2 mA/cm2) is 268.75 F/g (258 mF/cm2), which shows a dramatic improvement over the sum of the specific capacitances of pristine LMO (162.5 F/g) and pure rGO (29.94 F/g) electrodes in their relative ratios, when used alone. This finding suggests a synergistic coupling of LMO and rGO in the nanocomposite. We also assembled the LMO–rGO nanocomposite, as the positive electrode, with activated carbon, as the negative electrode, into an asymmetric cell configuration. The device shows an ultra-wide potential window of 2.0 V in a neutral aqueous Li2SO4 electrolyte, with a maximum energy density of 29.6 Wh/kg (which approaches the commercial lead-acid batteries), power density of up to 7408 W/kg, and an excellent cycle life (5% loss after 6000 cycles). These findings confirm that an LMO–rGO nanocomposite is a promising material to meet the demands of real world energy storage.  相似文献   

6.
It is possible to achieve high energy density and power density simultaneously for asymmetric supercapacitors by using pseudocapacitive materials with abundant ion intercalation/de-intercalation sites on the surface. Herein, a positive electrode based on feather-like MnO2 anchored on the activated carbon cloth is prepared, in which oxygen-enriched MnO2 nanorods with a radial sheet-like structure (OMO@AC) further form via electrochemical oxidation. Because of the large contact area with electrolyte and abundant oxidation functional groups on its surface, the OMO@AC displays excellent capacitance of 3,160 mF/cm2 at 1 mA/cm2. For the nitrogen-doped active carbon negative electrode, the capacitance is up to 1,875 mF/cm2 at 4 mA/cm2 due to the increase in disorder and defect on the carbon surface by N-doping. Furthermore, we verify the good electrochemical activity on the OMO@AC electrode surface by first-principles calculations and confirm the good matching degree between the positive and negative electrodes by CV testes. The aqueous oxygen-enriched MnO2// nitrogen-doped active carbon asymmetric supercapacitor exhibits an ultrahigh energy density of 8.723 mWh/cm3 at a power density of 14.248 mW/cm3 and display excellent cycle stability maintaining 95.5% after 10,000 cycles. The facile synthesis method and excellent performance provide a feasible way for the preparation of high-performance electrode materials for energy storage devices.  相似文献   

7.
High capacitance and high output voltage are two important research focuses of electrochemical supercapacitors. Herein we present two novel designs (laminated and tandem) of coin‐cell supercapacitors based on a textile coated with active material. The fabric electrodes were prepared by dipping the non‐woven cloth into a dispersion of carbon nanotubes and subsequent MnO2 electrodeposition. In the lamination configuration, several pieces of active‐material‐coated cloth were laminated to construct individual electrodes that enable fold‐increased areal capacitances and excellent cycling stability. In the tandem structure, individual cells with solid‐state electrolyte (polyvinyl alcohol/H3PO4) sandwiched between the fabric electrodes were stacked together to form a single device. The assembled device composed by ten unit cells was demonstrated to drive four LED digital screens in series with 10 V output.  相似文献   

8.
Along with high power capability and energy density, long cycle life is regarded an essential performance requirement for energy storage devices. The rapid capacitance decline of conducting polymer-based electrodes remains a major technical challenge and precludes their practical applications in supercapacitors. In this work, a polyaniline (PANI) network is synthesized via interfacial Buchwald–Hartwig polymerization for the first time, facilitating the construction of covalently connected PANI networks by ligand-promoted C–N bond formation. Particularly, the interfacial synthesis and subsequent gas release from pre-anchored protecting groups allow bottom-up and efficient access to porous cross-linked PANI (PCL-PANI) films that are free-standing and solvent-resistant. Upon assembling into supercapacitors, the PCL-PANI material enables an unprecedent long-term charge–discharge cycling performance (>18 000 times) without clear capacitance loss for an additive-free pseudocapacitive system. In addition, this synthesis affords electrodes entirely consisting of conducting polymers, yielding highly reversible gravimetric capacitance at 435 F gelectrode−1 in a two-electrode system, and a high gravimetric energy of 12.5 W h kgelectrode−1 while delivering an outstanding power density of 16 000 W kgelectrode−1, which is 10-fold higher than those of conventional linear PANI composite supercapacitors. This synthetic approach represents a novel and versatile strategy to generate additive/binder-free and high-performance conducting thin-films for energy storage.

A covalently cross-linked polyaniline network is synthesized via interfacial Buchwald-Hartwig polymerization/deprotection, enabling the generation of additive/binder-free and high-performance conducting thin-films for energy storage.   相似文献   

9.
Fabricating electrical double-layer capacitors (EDLCs) with high energy density for various applications has been of great interest in recent years. However, activated carbon (AC) electrodes are restricted to a lower operating voltage because they suffer from instability above a threshold potential window. Thus, they are limited in their energy storage. The deposition of inorganic compounds’ atomic layer deposition (ALD) aiming to enhance cycling performance of supercapacitors and battery electrodes can be applied to the AC electrode materials. Here, we report on the investigation of zinc oxide (ZnO) coating strategy in terms of different pulse times of precursors, ALD cycles, and deposition temperatures to ensure high electrical conductivity and capacitance retention without blocking the micropores of the AC electrode. Crystalline ZnO phase with its optimal forming condition is obtained preferably using a longer precursor pulse time. Supercapacitors comprising AC electrodes coated with 20 cycles of ALD ZnO at 70 °C and operated in TEABF4/acetonitrile organic electrolyte show a specific capacitance of 23.13 F g−1 at 5 mA cm−2 and enhanced capacitance retention at 3.2 V, which well exceeds the normal working voltage of a commercial EDLC product (2.7 V). This work delivers an additional feasible approach of using ZnO ALD modification of AC materials, enhancing and promoting stable EDLC cells under high working voltages.  相似文献   

10.
Scientific research is being compelled to develop highly efficient and cost-effective energy-storing devices such as supercapacitors (SCs). The practical use of SC devices is hindered by their low energy density and poor rate capability due to the binding agents in fabricating electrodes. Herein, we proposed flower-like highly open-structured binder-free ZnCo2O4 micro-flowers composed of nanosheets supported in nickel foam (ZnCoO@NF) with improved rate capability up to 91.8% when current varied from 2 to 20 A·g−1. The ZnCoO@NF electrode exhibited a superior specific capacitance of 1132 F·g−1 at 2 A·g−1 and revealed 99% cycling stability after 7000 cycles at a high current density of 20 A·g−1. The improved performance of the ZnCoO@NF electrode is attributed to the highly stable structure of the micro/nano-multiscale architecture, which provides both the high conduction of electrons and fast ionic transportation paths simultaneously.  相似文献   

11.
One common dilemma encountered in designing a supercapacitor electrode is that the specific capacitance (Cs) of the active material decreases significantly as the active-material loading (mass area? 1) increases. As a result, the geometric capacitance density (GCD; Farad area? 1) of the electrode does not scale up linearly but gradually levels off with increasing loading. For MnO2 supercapacitors, this problem has been solved to a great extent by introducing a superabsorbent polymer (SAP) binder, namely polyacrylic acid (PAA), to form composite particles with MnO2. Other than acting as a binder to bound together MnO2 particles, the SAP is believed to facilitate distribution of electrolyte throughout the active layer owing to its electrolyte-absorbing and swelling behaviors. The Cs of MnO2 remains almost unchanged as the oxide loading varies over a wide range (1.5–6.5 mg cm? 2) of heavy active-material loading. In addition, putting PAA throughout the entire active layer helps to magnify the specific interaction between PAA and MnO2 that is known to enhance the capacitance of individual MnO2 particles. The success in combining both high Cs and high active-material loading results in GCD of ca. 1.8–1.4 F cm? 2 even under very high current densities (ca. 35–260 mA cm? 2 or 5–40 A g? 1-MnO2).  相似文献   

12.
High-performance porous carbons derived from tea waste were prepared by hydrothermal treatment, combined together with KOH activation. The heat-treatment-processed materials possess an abundant hierarchical structure, with a large specific surface of 2235 m2 g−1 and wetting-complemental hydrophilicity for electrolytes. In a two-electrode system, the porous carbon electrodes’ built-in supercapacitor exhibited a high specific capacitance of 256 F g−1 at 0.05 A g−1, an excellent capacitance retention of 95.4% after 10,000 cycles, and a low leakage current of 0.014 mA. In our work, the collective results present that the precursor crafted from the tea waste can be a promising strategy to prepare valuable electrodes for high-performance supercapacitors, which offers a practical strategy to recycle biowastes into manufactured materials in energy storage applications.  相似文献   

13.
Fibers made from CNTs (CNT fibers) have the potential to form high-strength, lightweight materials with superior electrical conductivity. CNT fibers have attracted great attention in relation to various applications, in particular as conductive electrodes in energy applications, such as capacitors, lithium-ion batteries, and solar cells. Among these, wire-shaped supercapacitors demonstrate various advantages for use in lightweight and wearable electronics. However, making electrodes with uniform structures and desirable electrochemical performances still remains a challenge. In this study, dry-spun CNT fibers from CNT carpets were homogeneously loaded with MnO2 nanoflakes through the treatment of KMnO4. These functionalized fibers were systematically characterized in terms of their morphology, surface and mechanical properties, and electrochemical performance. The resulting MnO2–CNT fiber electrode showed high specific capacitance (231.3 F/g) in a Na2SO4 electrolyte, 23 times higher than the specific capacitance of the bare CNT fibers. The symmetric wire-shaped supercapacitor composed of CNT–MnO2 fiber electrodes and a PVA/H3PO4 electrolyte possesses an energy density of 86 nWh/cm and good cycling performance. Combined with its light weight and high flexibility, this CNT-based wire-shaped supercapacitor shows promise for applications in flexible and wearable energy storage devices.  相似文献   

14.
Polyoxometalates (POMs) demonstrate potential for application in the development of integrated smart energy devices based on bifunctional electrochromic (EC) optical modulation and electrochemical energy storage. Herein, a nanocomposite thin film composed of a vanadium-substituted Dawson-type POM, i.e., K7[P2W17VO62]·18H2O, and TiO2 nanowires were constructed via the combination of hydrothermal and layer-by-layer self-assembly methods. Through scanning electron microscopy and energy-dispersive spectroscopy characterisations, it was found that the TiO2 nanowire substrate acts as a skeleton to adsorb POM nanoparticles, thereby avoiding the aggregation or stacking of POM particles. The unique three-dimensional core−shell structures of these nanocomposites with high specific surface areas increases the number of active sites during the reaction process and shortens the ion diffusion pathway, thereby improving the electrochemical activities and electrical conductivities. Compared with pure POM thin films, the composite films showed improved EC properties with a significant optical contrast (38.32% at 580 nm), a short response time (1.65 and 1.64 s for colouring and bleaching, respectively), an excellent colouration efficiency (116.5 cm2 C−1), and satisfactory energy-storage properties (volumetric capacitance = 297.1 F cm−3 at 0.2 mA cm−2). Finally, a solid-state electrochromic energy-storage (EES) device was fabricated using the composite film as the cathode. After charging, the constructed device was able to light up a single light-emitting diode for 20 s. These results highlight the promising features of POM-based EES devices and demonstrate their potential for use in a wide range of applications, such as smart windows, military camouflage, sensors, and intelligent systems.  相似文献   

15.
Multi-layered electrodes which consist of polyaniline (PANI)/manganese dioxide (MnO2)-multi-walled carbon nanotubes (MWNTs) are prepared as the electrode materials for supercapacitors. MnO2-MWNTs are made by the in situ direct coating method to deposit MnO2 onto MWNTs; the core/shell structure of multi-layered fibrous electrodes can also be obtained by PANI coating onto the MnO2-MWNTs. The effect of PANI coating on the electrochemical performance and cyclic stability of MnO2-MWNTs is investigated. From the cyclic voltammograms, the PANI/MnO2-MWNTs show remarkably enhanced specific capacitance and cycle stability compared to MnO2-MWNTs, where the highest specific capacitance (350 F/g) is obtained at a current density of 0.2 A/g for the PANI/MnO2-MWNTs as compared to 92 F/g for pristine MWNTs and 306 F/g for MnO2-MWNTs. This indicates that the improved electrochemical performance of PANI/MnO2-MWNTs is due to the enhanced electrical properties by nano-scale-coated MnO2 onto MWNTs and the PANI coating that leads to the increased cycle stability by delaying the dissolution of MnO2 during charge/discharge tests.  相似文献   

16.
A simple and novel methodology was developed for manufacturing interdigitated asymmetric all-solid-state flexible micro-supercapacitors (MSCs) by a facile pencil drawing process followed by electrodepositing MnO2 on one of the as-drawn graphite electrode as anode and the other as cathode.  相似文献   

17.
A conjugated copper(II) catecholate based metal–organic framework (namely Cu‐DBC) was prepared using a D2‐symmetric redox‐active ligand in a copper bis(dihydroxy) coordination geometry. The π‐d conjugated framework exhibits typical semiconducting behavior with a high electrical conductivity of ca. 1.0 S m?1 at room temperature. Benefiting from the good electrical conductivity and the excellent redox reversibility of both ligand and copper centers, Cu‐DBC electrode features superior capacitor performances with gravimetric capacitance up to 479 F g?1 at a discharge rate of 0.2 A g?1. Moreover, the symmetric solid‐state supercapacitor of Cu‐DBC exhibits high areal (879 mF cm?2) and volumetric (22 F cm?3) capacitances, as well as good rate capability. These metrics are superior to most reported MOF‐based supercapacitors, demonstrating promising applications in energy‐storage devices.  相似文献   

18.
Micro/mesoporous carbon was prepared by chlorination of ordered mesoporous silicon carbide derived from magnesio-thermal reduction of templated carbon-silica precursors. These materials were then used as active materials for electrochemical capacitors and characterized in 1.5 M NEt4BF4/AN. The electrodes showed outstanding rate capability (90% of capacity retention at 1 V/s and time constant of 1 s) with high specific areal capacitance (0.5 F/cm2 of electrode), that makes such hierarchical porous carbons promising for high power and energy density supercapacitors.  相似文献   

19.
A 3D hierarchical carbon cloth/nitrogen-doped carbon nanowires/Ni@MnO2 (CC/N-CNWs/Ni@MnO2) nanocomposite electrode was rationally designed and prepared by electrodeposition. The N-CNWs derived from polypyrrole (PPy) nanowires on the carbon cloth have an open framework structure, which greatly increases the contact area between the electrode and electrolyte and provides short diffusion paths. The incorporation of the Ni layer between the N-CNWs and MnO2 is beneficial for significantly enhancing the electrical conductivity and boosting fast charge transfer as well as improving the charge-collection capacity. Thus, the as-prepared 3D hierarchical CC/N-CNWs/Ni@MnO2 electrode exhibits a higher specific capacitance of 571.4 F g−1 compared with those of CC/N-CNWs@MnO2 (311 F g−1), CC/Ni@MnO2 (196.6 F g−1), and CC@MnO2 (186.1 F g−1) at 1 A g−1 and remarkable rate capability (367.5 F g−1 at 10 A g−1). Moreover, asymmetric supercapacitors constructed with CC/N-CNWs/Ni@MnO2 as cathode material and activated carbon as anode material deliver an impressive energy density of 36.4 W h kg−1 at a power density of 900 W kg−1 and a good cycling life (72.8 % capacitance retention after 3500 cycles). This study paves a low-cost and simple way to design a hierarchical nanocomposite electrode with large surface area and superior electrical conductivity, which has wide application prospects in high-performance supercapacitors.  相似文献   

20.
Novel polyacrylamide gel electrolytes (PGEs) doped with nano carbons with enhanced electrochemical, thermal, and mechanical properties are presented. Carboxylated carbon nanotubes (fCNTs), graphene oxide sheets (GO), and the hybrid of fCNT/GO were embedded in the PGEs to serve as supercapacitor (SC) electrolytes. Thermal stability of the unmodified PGE increased with the addition of the nano carbons which led to lower capacitance degradation and longer cycling life of the SCs. The fCNT/GO-PGE showed the best thermal stability, which was 50% higher than original PGE. Viscoelastic properties of PGEs were also improved with the incorporation of GO and fCNT/GO. Oxygen-containing functional groups in GO and fCNT/GO hydrogen bonded with the polymer chains and improved the elasticity of PGEs. The fCNT-PGE demonstrated a slightly lower viscous strain uninform distribution of CNTs in the polymer matrix and the defects formed within. Furthermore, ion diffusion between GO layers was enhanced in fCNT/GO-PGE because fCNT decreased the aggregation of GO sheets and improved the ion channels, increasing the gel ionic conductivity from 41 to 132 mS cm−1. Finally, MnO2-based supercapacitors using PGE, fCNT-PGE, GO-PGE, and fCNT/GO-PGE electrolytes were fabricated with the electrode-specific capacitance measured to be 39.5, 65.5, 77.6, and 83.3 F·g−1, respectively. This research demonstrates the effectiveness of nano carbons as dopants in polymer gel electrolytes for property enhancements.  相似文献   

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