Composites For Supercapacitors Research Articles

In situ tracking of hydrodynamic and viscoelastic changes in electrophoretically deposited LiFePO4 electrodes during their charging/discharging

Electrophoretically deposited (EPD) lithium ferrophosphate (LFP) electrodes (LiFePO4) containing either soft Mg(OH)2 or rigid PVdF binders have been fabricated and tested in Li2SO4 aqueous solution. The use of Electrochemical Quartz-Crystal Microbalance with dissipation monitoring (EQCM-D) was shown to be extremely advantageous to distinguish between the effectively viscoelastic and rigid states of LFP and LFP/PVdF electrodes, respectively, based already on the raw EQCM-D (i.e. recording resonant frequency and resonance width changes of the electrode on multiple overtone orders). The approach that we developed for testing composite battery and supercapacitor electrodes is quite general, and includes mechanical characterizations of the electrodes in air, in contact with liquids and electrolyte solutions, and most importantly, during combined electrochemical and mechanical characterization of battery electrodes subjected to Li-ions insertion/extraction. A new theory of hydrodynamic admittance of porous semispherical bumps has been developed and successfully applied for the characterization of rigid porous LFP/PVdF composite electrode in its both intercalated and deintercalated states. We show that the extended Voight-type viscoelastic model describes quantitatively the intercalated and deintercalated states of LFP electrode coating containing soft Mg(OH)2 binder. The approach based on non-gravimetric application of EQCM-D developed in this work is unique and quite promising for in-situ mechanical characterization of a large variety of battery and supercapacitor electrodes for energy-storage devices.

Highly stable 2,3,5,6-tetrachloro-1,4-benzoquinone electrodes for supercapacitors

Carbon materials have enjoyed wide applications in supercapacitors because of their high surface area which guarantees a high power output through the formation of an electric double layer (EDL). However the energy stored by this EDL mechanism is often insufficient and as such there is the need to upgrade them for higher energy applications. Quinone materials are attracting interest because of their pseudocapacitance contributions which help to boost the energy density of supercapacitors. In this study, composite supercapacitor electrodes are prepared by mechanically mixing 2,3,5,6-tetrachloro-1,4-benzoquinone (TCBQ) and activated carbon. An investigation of 5% w/w and 10% w/w of this quinolic material as a pseudocapacitance material to activated carbon in 1M HCl aqueous electrolyte delivers a specific capacitance of 236Fg−1 and 240Fg−1 comparable to 190Fg−1 of just activated carbon over a potential range of −0.3V–0.9V vs Ag+/Ag. Contrary to what is commonly observed, this material is highly insoluble in the electrolyte medium and remains stable with cycling, recovering 99.57% (for 10% w/w addition) and 99.13% (for 5% w/w addition) of its initial capacitance after cycling at 500mVs−1 scan rate. The findings in this report potentially provides a cheaper yet efficient route to boost the energy density of activated carbon using TCBQ for high energy supercapacitor applications.

Fabrication of novel solid-state supercapacitor using a Nafion polymer membrane with graphene oxide/multiwalled carbon nanotube/polyaniline

In the current work, the effect of aniline concentration on the polymerization process and supercapacitive behavior of graphene oxide/multiwalled carbon nanotubes/polyaniline (GMP) nanocomposites were studied. Based on the obtained results, GMP nanocomposite with 0.5 M aniline (GMP5) was selected as the optimum concentration in terms of high current density and high specific capacitance. Nafion-based ionic polymer-free metal composite (IPFMC) supercapacitor was fabricated for the GMP5 nanocomposite. Solid-state symmetric supercapacitor was made after spraying of GMP5 in. on both sides of Nafion membrane. The electrochemical properties were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge (CD), and electrochemical impedance spectroscopy (EIS) techniques in 0.5 M Na2SO4.The specific capacitance of 383.25 F g−1 (326 mF cm−2) and 527.5 F g−1 (42 mF cm−2) was obtained for the GMP5 in solid-state supercapacitor and three-electrode cell at a scan rate of 10 mV s−1, respectively. The maximum energy and power densities of 53.64 and 1777.4 W kg−1 were obtained for the IPFMC-based supercapacitor.

Polypyrrole/carbon nanotube supercapacitors: Technological advances and challenges

Abstract The supercapacitors are advanced electrochemical energy storage devices having characteristics such as high storage capacity, rapid delivery of charge, and long cycle life. Polypyrrole (PPy) – an electronically conducting polymer, and carbon nanotubes (CNT) with high surface area and exceptional electrical and mechanical properties are among the most frequently studied advanced electrode materials for supercapacitors. The asymmetric supercapacitors composed of PPy/CNT composite electrodes offer complementary benefits to improve the specific capacitance, energy density, and stability. This article presents an overview of the recent technological advances in PPy/CNT composite supercapacitors and their limitations. Various strategies for synthesis and fabrication of PPy/CNT composites are discussed along with the factors that influence their ultimate electrochemical performance. The drawbacks and challenges of modern PPy/CNT composite supercapacitors are also reviewed, and potential areas of concern are identified for future research and development.

Wrinkled graphene — carbon nanospheres composite for ultra high energy supercapacitors

ABSTRACTA simple and scalable method is developed to prepare highly wrinkled graphene sheets – carbon nanospheres (WG-CN) composite for ultra high energy density supercapacitor application. Here, we introduce a novel simple paraffin wax candle flame technique for the simultaneous reduction of graphene oxide (GO) and deposition of carbon nanospheres on the graphene sheets. This is followed by introducing permanent wrinkles to the composite. The WG-CN composite exhibit the high specific capacitance values of 290 F g-1 and 253.7 F g-1 (138.5 F cm-3) for 6M KOH and EMIMBF4 ionic liquid electrolytes respectively. The ultra high energy density values of 108 Wh Kg-1 and 58.9 Wh L-1 has been obtained at the power density of 3955 W Kg-1 and 2157 W L-1 simultaneously. These attractive performances exhibited by the WG-CN composite supercapacitor electrode make them potential candidate for future energy storage devices. The key to success of this composite is the ability to make full utilization of the high intrinsic specific surface area of the nanocomposite.

Large-Scale Production of Large-Size Atomically Thin Semiconducting Molybdenum Dichalcogenide Sheets in Water and Its Application for Supercapacitor.

To progress from laboratory research to commercial applications, it is necessary to develop an effective method to prepare large quantities and high-quality of the large-size atomically thin molybdenum dichalcogenides (MoS2). Aqueous-phase processes provide a viable method for producing thin MoS2 sheets using organolithium-assisted exfoliation; unfortunately, this method is hindered by changing pristine semiconducting 2H phase to distorted metallic 1T phase. Recovery of the intrinsic 2H phase typically involves heating of the 1T MoS2 sheets on solid substrates at high temperature. This has restricted and hindered the utilization of 2H phase MoS2 sheets suspensions. Here, we demonstrate that the synergistic effect of the rigid planar structure and charged nature of organic salt such as imidazole (ImH) can be successfully used to produce atomically thin 2H-MoS2 sheets suspension in water. Moreover, lateral size and area of the exfoliated sheet can be up to 50 μm and 1000 μm2, respectively. According to the XPS measurements, nearly 100% of the 2H-MoS2 sheets was successfully prepared. A composite paper supercapacitor using the exfoliated 2H-MoS2 and carbon nanotubes delivered a superior volumetric capacitance of ~410 F/cm3. Therefore, the organic salts-assisted liquid-phase exfoliation has great potential for large-scale production of 2H-MoS2 suspensions for supercapacitor application.

ZCO/CNT Composites Coated on Silver Substrates as Symmetric Supercapacitor and their Dielectrics Characterization at Various Frequencies

<span>Supercapacitor is a high power density energy storage device which complements the lack of <span>batteries and conventional capacitors. One material which has a great potential in the <span>manufacture of composite supercapacitor is spinel ZnCo<span>2<span>O<span>4<span>/carbon nano tube and abreviated in <span>the later case as ZCO/CNT. Composition variations in ZCO/CNT composites is expected to the <span>performance of supercapacitor especially the dielectric properties and specific capacitance. In<br /><span>this study the composite ZCO/CNT was made from raw materials of ZCO nano crystal which <span>was prepared from previous research on which employing sonochemistry technic, carbon nano <span>tube, and 1-methil 2 pyrolidine. A screen printing method was used in this experiment to <span>deposite the composite on silver substrates. The separator in between of two identical composite <span>structures was prepared from isotactic polypropylene. We used KOH 6 M which was <span>implemented as electrolyte of the composites. Characterization of composite structures has been <span>performed using X-RD, while the morphology characterization using SEM. It was found that the <span>dielectric supercapacitor increase by increasing of mass fraction of ZCO in the composite. The<br /><span>highest dielectric constant is reached at 1.89 x 10<span>6 <span>and the specific capacitance of 81 F/g for 3:1<span>mass ratio of ZCO : CNT at 100 Hz.</span></span></span></span></span></span></span></span></span></span></span></span></span></span><br /></span></span></span></span></span></span></span>

Supercapacitors: A Fiber Supercapacitor with High Energy Density Based on Hollow Graphene/Conducting Polymer Fiber Electrode (Adv. Mater. 19/2016)

Hollow fiber electrodes based on graphene/conducting polymer are developed by J. Cheng, B. Wang, H. Peng, and co-workers to fabricate novel and high-performance fiber-shaped supercapacitors. As described on page 3646, the hollow composite fiber supercapacitors have an ultra-high specific capacitance of 304.5 mF cm−2 and an ultra-high energy density of 27.1 μW h cm−2 at a power density of 66.5 μW cm−2. These mechanical and electrochemical properties make the fiber supercapacitors a promising material for next-generation wearable electronics.

The Composite Supercapacitor

AbstractInspired by the design of composite materials, we propose a new composite supercapacitor that comprises an integrated cell with high‐power‐ and high‐energy‐related electrode materials. The composite electrochemical double‐layer capacitor (EDLC) is the equivalent circuit of a high‐power EDLC of power P1 and energy E1 and a high‐energy EDLC of power P2 and energy E2 connected in parallel. A methodology is proposed and validated in this study for the design of an application‐specific composite supercapacitor of power P and energy E with P1/E1>P/E>P2/E2. The methodology was tested successfully in medium‐ and large‐sized application‐specific composite supercapacitors, which were fabricated in the form of pouch cells using an organic electrolyte. The application‐specific composite supercapacitors offered weight reductions of 40–60 % compared with supercapacitors based on the high‐power‐ or on high‐energy‐related electrode materials only.

Rationally Designed Carbon Fiber@NiCo2O4@Polypyrrole Core–Shell Nanowire Array for High-Performance Supercapacitor Electrodes

The composite supercapacitor electrodes were rationally fabricated by facile electrochemical deposition of polypyrrole (PPy) on NiCo2O4 nanowire arrays which were grown radially on carbon fiber (CF). When used as electrodes in supercapacitors, the composite nanostructures demonstrated prominent electrochemical performances with a high areal capacitance (1.44[Formula: see text]F/cm2 at a current density of 2[Formula: see text]mA/cm2), a good rate capability (80.5% when the current density increases from 2[Formula: see text]mA/cm2 to 20[Formula: see text]mA/cm2), and a good cycling ability (85% of the initial specific capacitance remained after 5000 cycles at a high current density of 10[Formula: see text]mA/cm2). The excellent electrochemical performance of NiCo2O4@PPy nanostructures can be mainly ascribed to the good electrical conductivity of PPy, the enhanced adherent force between electrode materials and CF to hold the electrode fragments together by means of NiCo2O4 nanowires, the short ion diffusion pathway in ordered porous NiCo2O4 nanowires and the three-dimensional nanostructures.

Polyoxometalates@Metal-Organic Frameworks Derived Porous MoO3@CuO as Electrodes for Symmetric All-Solid-State Supercapacitor

The demand of uniformity and porosity for composite supercapacitor material has triggered tremendous research efforts for the development of doping method. Herein, we report an effective strategy for homogeneous and polyporous MoO3@CuO composite by heating a POMs@MOFs template (POMs=polyoxometalates, MOFs=Metal-organic frameworks), in which the Mo-POMs are incorporated into Cu-MOFs as secondary building units. The excellent doping of MoO3 to CuO leads to an obvious improvement in specific discharge capacity (from 15.4mAhg−1 for CuO to 86.3mAhg−1 for MoO3@CuO). The layered structure of MoO3 plays a key role in providing facilitated ion transport and electron diffusion pathways for the composite material. This electrode demonstrates excellent electrochemical performance with a specific discharge capacity of 86.3mAhg−1at 1Ag−1 in 1M LiOH. When this porous MoO3@CuO electrode is assembled into a symmetric all-solid-state device with PVA-LiOH gel polymer, the as-fabricated device demonstrates good performance with an energy density of 7.9Whkg−1, power density of 8726Wkg−1, and excellent cycle life. This work presents a new template to improve the uniformity and porosity of composite metal oxides, which can be used for high-performance supercapacitors.

Facile fabrication of Co2CuS4nanoparticle anchored N-doped graphene for high-performance asymmetric supercapacitors

A novel Co2CuS4/NG composite based asymmetric supercapacitor delivers superb energy density (~53.3 W h kg−1), high power density (~10936 W kg−1at 38.4 W h kg−1) and outstanding cycling stability (~4000 cycles).

One-step process to form a nickel-based/carbon nanofoam composite supercapacitor electrode using Na2SO4 as an eco-friendly electrolyte

Anodic electrodeposition of NiOx (NiO + NiOOH) onto carbon nanofoam forming a supercapacitor electrode. The resulting composite electrode operates at 2.2 V in Na2SO4 aqueous medium.

Electrostatic assembly of composite supercapacitor electrodes, triggered by charged dispersants

Advanced MnO2–carbon nanotube electrodes for supercapacitors were fabricated by self-assembly using cationic and anionic dispersants with selective adsorption.

Multi-channeled hierarchical porous carbon incorporated Co3O4 nanopillar arrays as 3D binder-free electrode for high performance supercapacitors

3D hierarchical carbon-based nanostructures not only create hierarchical porous channels, but also possess high electrical conductivity and maintain excellent structural mechanical stability for high-performance supercapacitors. In this research, hierarchical porous N-doped carbon and Co3O4 nanopillar arrays derived from Morpho butterfly wing scales have been explored. These structures have demonstrated enhanced capacitance, with a maximum specific capacity of 978.9Fg−1 at 0.5Ag−1, and good cycling stability, retaining about 94.5% of their capacitance after 2000 cycles as well as improving supercapacitor energy density without sacrificing power density. The maximum energy density of the carbonized wing scale-cobalt oxide (CWs-Co3O4) composite supercapacitors was found to be 99.11Whkg−1. This paper proposes a method for building 3D hierarchical N-doped carbon materials with various morphologies. It also presents a concept and method for designing a carbon-based 3D binder-free electrode with a hierarchical structure. This research provides a vast structural pool for developing novel electrochemical properties based on these materials.

A 1 V supercapacitor device with nanostructured graphene oxide/polyaniline composite materials

Polyaniline and graphene oxide composite on activated carbon cum reduced graphene oxide-supported supercapacitor electrodes are fabricated and electrochemically characterized in a three-electrode cell assembly. Attractive supercapacitor performance, namely high-power capability and cycling stability for graphene oxide/polyaniline composite, is observed owing to the layered and porous-polymeric-structured electrodes. Based on the materials characterization data in a three-electrode cell assembly, 1 V supercapacitor devices are developed and performance tested. A comparative study has also been conducted for polyaniline and graphene oxide/polyaniline composite-based 1 V supercapacitors for comprehending the synergic effect of graphene oxide and polyaniline. Graphene oxide/polyaniline composite-based capacitor that exhibits about 100 F g−1 specific capacitance with faradaic efficiency in excess of 90% has its energy and power density values of 14 Wh kg−1 and 72 kW kg−1, respectively. Cycle-life data for over 1000 cycles reflect 10% capacitance degradation for graphene oxide/polyaniline composite supercapacitor.

Electrophoretically deposited graphene oxide and carbon nanotube composite for electrochemical capacitors

We report a scalable one-step electrode fabrication approach for synthesizing composite carbon-based supercapacitors with synergistic outcomes. Multi-walled carbon nanotubes (MWCNTs) were successfully integrated into our modified electrophoretic deposition process to directly form composite MWCNT–GO electrochemical capacitor electrodes (where GO is graphene oxide) with superior performance to solely GO electrodes. The measured capacitance improved threefold, reaching a maximum specific capacitance of 231 F g−1. Upon thermal reduction, MWCNT–GO electrode sheet resistance decreased by a factor of 8, significantly greater than the 2× decrease of those without MWCNTs.

Effect of temperature on pseudocapacitance performance of carbon fiber@NiCo2O4@Ni(OH)2 core–shell nanowire array composite electrodes

The composite supercapacitor electrodes are fabricated by facile electrochemical deposition of Ni(OH)2 nanosheets on NiCo2O4 nanowire arrays which are grown radially on carbon fiber. The composite electrodes offer specific capacitance of 2400F/g at 1mA/cm2, excellent rate capability of 89% as the current density increasing from 1 to 20mA/cm2. Electrochemical performances are investigated at different temperatures from 0°C to 60°C. The specific capacitance at 1mA/cm2 increases from 2100F/g at 0°C to 3000F/g at 60°C. The mechanisms of effect of temperature on the electrochemical properties of the composite electrode are investigated. This study provides a fundamental comprehension of the temperature dependent of composite electrodes.

Effects of Surfactant and Calcining Temperature on Capacitive Properties of Co3O4/graphene Compositesfor Supercapacitors

Effects of Surfactant and Calcining Temperature on Capacitive Properties of Co3O4/graphene Compositesfor Supercapacitors

Viscoelastic potential-induced changes in acoustically thin films explored by quartz crystal microbalance with motional resistance monitoring

Viscoelastic properties of intrinsically conducting polymers depend on different factors, among them polymer structure, ionic and solvent population and film thickness. During a voltammetric cycle, electrochemical reactions involve changes of these factors. Consequently, the viscoelastic properties are expected to be changed. Electrochemical quartz crystal microbalance with motional resistance monitoring were employed to calculate the instantaneous resonant frequency/motional resistance ratio (dfr/dRm)during the electrochemical processes of acoustically thin films of poly(o-toluidine). dfr/dRm is defined as the energy dissipation factor and shows values around ∼10HzΩ−1 for a net liquid-loading effect on resonator electrode. Therefore, as this value is larger the film deposited on resonator electrode is expected to be more rigid. The experimental results showed in this work points to this assumption. Viscoelastic state of acoustically thin films of poly(o-toluidine) were investigated through redox reactions, in different electrolytes and scan rates potential perturbations. Finally, viscoelastic changes of a relaxed POT and packed POT was compared. The viscoelastic aspects of poly(o-toluidine) here investigated can help to understand and adjust the signal transduction of (bio) sensors or for composite supercapacitors where the mechanical properties of the different organic layers can limit the performances of the electrochemical system.