High Specific Capacitance Value Research Articles

Preparation of highly conductive metal doped/substituted Li7P2S8Br(1-x)Ix type lithium superionic conductor for all-solid-state lithium battery applications

Sulfide-based lithium superionic conducting solid electrolytes for all-solid-state lithium batteries have received much attention due to their high safety, ionic conductivity, and compatibility. However, high-temperature treatment over a long time is needed to achieve high ionic conductivity. In this work, we have prepared the dual-halide-based Li7P2S8X type lithium superionic conductors by dry ball mill process and the high ionic conducting phase was achieved by low temperature (200℃) heat-treatment process. High ionic conducting halogen-halogen composition was arrived at through a series of optimization processes. Among the compositions tested, the Li7P2S8Br0.25I0.75 solid electrolyte exhibited a high ionic conductivity value of 6.16 mS cm−1, at room temperature. The ionic radius of the halogen element played an important role in the formation of the high ionic conducting phase. Further, the ionic conductivity of Li7P2S8I0.75Br0.25 solid electrolyte was improved by metal doping at P-site. The Sn-doped Li7P2S8I0.75Br0.25 solid electrolyte exhibited a high ionic conductivity value of 7.78 mS cm−1, at room temperature. The addition of large-sized Sn atoms extended the crystal lattice parameters and increased the Li-ions transport path. The partial substitution of Sn atoms at P-site was confirmed by NMR and Laser Raman analysis. The electrochemical stability of the prepared solid electrolyte was studied by cyclic voltammetry and DC charge-discharge analysis. The addition of a metal atom to the Li7P2S8Br0.25I0.75 solid electrolyte decreased the side reaction with the Li metals. Thus, low-temperature treated metal-doped Li7P2S8Br0.25I0.75 solid electrolytes are highly favourable for the fabrication of high-performance all-solid-state batteries. The fabricated all-solid-state battery using Sn doped Li7P2S8Br0.25I0.75 solid electrolyte exhibited the high specific capacity value of 170 mAh g−1 (0.1C), at room temperature.

Tuning the surface functionalities, textural properties and capacitance properties of reduced graphene oxide by utilizing environmentally threatening invasive weed as a reducing agent

In general, reduced graphene oxide (RGO) is prepared by conventional chemical methods using various reducing agents. The quality and properties of RGO depend on extend of exfoliation and the nature of the reducing agent used for the reduction of graphene oxide (GO). In this work, GO is prepared by modified Hummers’ method and subsequent ultrasonic exfoliation. Then it is hydrothermally reduced to RGO using different amounts (0, 5, 10, 20 and 30 mL) of ethanolic extract of the environmentally threatening invasive weed, Prosopis juliflora. The ethanolic extract of the weed plays multiple roles: (i) reducing GO, (ii) doping nitrogen and (iii) incorporating spacer. The textural properties and surface functionalities (oxygen and nitrogen-based) and thus the capacitance properties of RGO largely depend on the amount of ethanolic extract of the weed used to reduce GO. RGO obtained by reducing GO using a different amount of ethanolic extract of the weed is referred to as RGOXE, where X refers to the amount of ethanolic extract of the weed. The value of specific capacitance follows the order: RGO10E (170 F g − 1) > RGO5E (160 F g − 1) > RGO20E (112 F g − 1) > RGO30E (98 F g − 1) > pristine GO (88 F g − 1). Besides the high value of specific capacitance, RGO10E demonstrates good rate capability (retains 67% of its initial specific capacitance value on increasing the current density from 0.5 to 10 A g − 1) and stable cycle-life (retention of 100% specific capacitance for the tested number of 10,000 cycles). In addition, symmetric supercapacitor fabricated using RGO10E delivers energy density of 4.9 Wh kg−1 at a power density of 496 W kg−1.

Flax-Derived Carbon: A Highly Durable Electrode Material for Electrochemical Double-Layer Supercapacitors.

Owing to their low cost, good performance, and high lifetime stability, activated carbons (ACs) with a large surface area rank among the most popular materials deployed in commercially available electrochemical double-layer (EDLC) capacitors. Here, we report a simple two-step synthetic procedure for the preparation of activated carbon from natural flax. Such ACs possess a very high specific surface area (1649 m2 g–1) accompanied by a microporous structure with the size of pores below 2 nm. These features are behind the extraordinary electrochemical performance of flax-derived ACs in terms of their high values of specific capacitance (500 F g–1 at a current density of 0.25 A g–1 in the three-electrode setup and 189 F g–1 at a current density of 0.5 A g–1 in two-electrode setup.), high-rate stability, and outstanding lifetime capability (85% retention after 150,000 charging/discharging cycles recorded at the high current density of 5 A g–1). These findings demonstrate that flax-based ACs have more than competitive potential compared to standard and commercially available activated carbons.

Synthesis of graphene-like porous carbon from biomass for electrochemical energy storage applications

Graphene-like porous carbon (GLC) was synthesized from walnut shell (WSh) by carbonization and thermochemical activation process. The obtained samples of graphene-like porous carbon based on walnut shell (GLC-WSh) were characterized by physicochemical analysis in order to optimize the synthesis process. The optimum condition of GLC-WSh synthesis was determined to meet the basic requirements for various applications such as an active material for supercapacitors, lithium-ion battery, as energy-intensive additives in order to increase the efficiency of high-energy rocket fuels, and as a membrane for desalination of seawater. The Raman spectra confirmed the presence of few-layer graphene in GLC-WSh with on average number of 5–7 graphene layers. The specific surface area (SSA) was determined using nitrogen adsorption/desorption analysis. The SSA is 2800 m2 g−1 according to Brunauer-Emmett-Teller method. The mass yield of GLC-WSh from the initial mass of the WSh was 21%. The synthesized GLC-WSh powder was applied as an active material for an electrochemical double layer capacitor. Electrochemical characterization showed a high specific capacitance value of 263 F/ g and columbic efficiency of 99.4% at a gravimetric current density of 1000 mA/ g.

All-solid-state Na+ ion supercapacitors using Na3Zr2Si2PO12-polymer hybrid films as electrolyte

We report all-solid-state Na+ ion electrical double layer capacitors (EDLCs) for the first time in this study. These are fabricated using a novel Na+ ion solid polymer electrolyte (SPE) and high surface area (877 m2-g−1) activated carbon electrodes. Using salt (NaI), polyethylene oxide (PEO) and nano particles of Na3Zr2Si2PO12 (NZSP), hybrid electrolyte films with compositions 10NaI-90[PEO1-xNZSPx], where 0 ≤ x ≤ 0.7 are synthesized by a novel milling assisted route. The freestanding flexible film for x = 0.7 exhibits a maximum ionic conductivity of ~ 10−4 Ω−1 cm−1 at room temperature. The 2032 type EDLC with graphite current collector and polymer electrolyte film of composition x = 0.4 exhibits notably high value of specific capacitance (~ 104 F-g−1), and specific energy (~ 44 Wh-Kg−1) with a voltage stability window of ~ 2 volts. The NZSP content in the electrolyte influence the EDLC performance. The EDLCs with graphite sheet as current collector offer superior performance as compared to copper. Galvanostatic charge-discharge studies suggest stability of these supercapacitors at least upto ~ 400 cycles.

Optimizing the sulfur precursor for the synthesis of NiCo2S4 nanoparticles as high performance supercapacitor electrodes

In this report, NiCo2S4 nanoparticles (NPs) are successfully synthesized by a simple cost effective one step hydrothermal method using dissimilar sulfur sources (thiourea- NTU, thioacetamide- NTA) separately. The influence of sulfur source on structure, morphological, surface area and electrochemical performance are examined carefully. The X-Ray Diffraction Pattern of both samples displays the cubic phase of spinel NiCo2S4 crystal structures. TEM studies reveal Uniform Spherical (19–21 nm) and spheroidal (22–23 nm) shaped NPs. XPS spectra of both sample conforms the coexistence of Ni3+ and Ni2+ valence states of spinel cubic NiCo2S4. The surface area of NTA- NiCo2S4 found superior (91.23 m2 g−1) than NTU- NiCo2S4 (43.12 m2 g−1). The Electrochemical performance of NTA based NiCo2S4/Ni foam electrode results in showing high specific capacity values of 1051.49 C g−1 (292 m A h g−1) compare with NTU- NiCo2S4 (690 C g−1/191 m A h g−1) at a current density of 2 A g−1 moreover, NTA- NiCo2S4 holds exceptional Capacity retention of 98 % after 10,000 GCD cycles at current density of 6 A g−1 with excellent energy density of 88.377 W h Kg−1 with power density of 2179.15 W kg−1. The admirable electrochemical performance of NTA- NiCo2S4 brings out potential anticipation in supercapacitor applications.

Fabrication of Ni2O3–NiCx core–shell nanoparticles on fluorine-doped tin oxide electrodes via oxygen feeding from SnO2 under hydrogen conditions and their electrochemical performance as supercapacitors

The successful synthesis of Ni2O3–NiCx on SnO2/glass electrodes by a combined liquid/liquid interfacial reaction and low-temperature pyrolysis process under hydrogen gas conditions, is reported. The prepared samples were analyzed by various characterization tools. To evaluate the performances of the Ni2O3–NiCx on SnO2/glass electrodes as supercapacitors, cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), cycle stability and electrochemical impedance spectroscopy (EIS) were also carried out the Ni2O3–NiCx core-shell-structured electrode displayed supercapacitive behavior in 1.0 M KOH with a high specific capacitance value of 796 F g−1 and a relatively good rate capability at high current densities. Moreover, it also exhibited remarkable cycle stability, this research provides a valuable and effective approach to enhance the performance of materials applied as supercapacitors.

Hollow C-LDH/Co9S8 nanocages derived from ZIF-67-C for high- performance asymmetric supercapacitors

The design of supercapacitor electrode materials greatly depends on the rational construction of nanostructures and the effective combination of different active materials. Due to the poor electrical conductivity and mechanical strength, nickel-cobalt double hydroxide (NiCo-LDH) cannot reach the theoretical high specific capacitance value, while Co9S8 shows many interesting features, such as excellent electrochemical properties, high conductivity, and greatly improved redox reactions. Therefore, we prepared ZIF-67-C derived hollow NiCo-LDH (C-LDH)/Co9S8 nanocages containing two components of Co9S8 and NiCo-LDH through a multistep transformation method. The prepared C-LDH/Co9S8 nanoparticles showed a hollow rhomboid dodecahedron structure, and many NiCo-LDH nanosheets were reasonably distributed on the surface. In the three-electrode test, it can be obtained that its specific capacitance is 1654 F·g−1 when current density is 2 A·g−1 and 82.5% capacitance retention after 5000 cycles. Moreover, asymmetric supercapacitors (ASCs) prepared with C-LDH/Co9S8 as cathode and AC as anode can achieve a large energy density of 47.3 Wh·kg−1 under the condition of high power density of 1505 W·kg−1. After 10,000 cycles, capacitance retention rate is 80.9%, exhibit excellent cycle performance, suggesting the great potential of hollow C-LDH/Co9S8 nanocages in the application of supercapacitors.

Investigation of electrochemical performance of an efficient Ti2O3–CeO2 nanocomposite for enhanced pollution-free energy conversion applications

The development of an economical, abundant, stable, and greatly active electrocatalyst for water oxidation is extremely important for future energy conversion system. Electrochemical water splitting is a new move toward H2 and O2 gas production. It can be used in sustainable and pollution-free energy conversion applications. In this work, Ti2O3–CeO2 nanocomposites were successfully synthesized with different molar ratios by facile hydrothermal method for electrochemical water oxidation. Mixed phase structure of Ti2O3–CeO2 nanocomposites was confirmed by X-ray diffraction spectra and well identified by highest peak of Ti2O3 in 2θ values of 33.0 and CeO2 in 2θ values of 28.5. The characteristic peaks from Raman and photoluminescence spectroscopy further confirmed Ti2O3–CeO2 nanocomposite formation. Existence of multidimensional nanostructures such as nanoparticles and small nanocubes of Ti2O3–CeO2 nanocomposites were investigated by scanning electron microscope images. Mesoporous nature of Ti2O3–CeO2 nanocomposites was further analyzed by Brunauer–Emmett–Teller analysis. The high surface area could benefit the Ti2O3–CeO2 nanocomposites with greatly improved oxygen evolution reaction (OER) performance. In three molar ratios, 1:3 M ratios of Ti2O3–CeO2 nanocomposites showed high catalytic action at overpotential of 244 mV. The best OER electrocatalyst was obtained by 1:3 M ratios of Ti2O3–CeO2 nanocomposites, which exhibited high current density and high specific capacitance values of 238 mA/g and 517 F/g, respectively. Therefore, Ti/Ce molar ratio played a crucial role in enhancing the OER performance.

Comprehensive study to ascertain the effect of MnO2 loading on supercapacitive properties of conducting polymers

This study reports the electrochemical properties of Manganese dioxide (MnO2) with four types of conducting polymers such as polyaniline (PANi), polythiophene (PTh), polypyyrole, and polyindole (PIn) by preparing their composites. All four conducting polymers were prepared by chemical oxidative polymerization approach. The prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy, ultra–violate visible (UV–VIS) spectroscopy, and photoluminance (PL). Similarly, the supercapacitive properties such, cyclic voltammetry (CV) curve, capacitance retention and cycle stability of composite materials were investigated. The highest value of specific capacitance was obtained for MnO2-PANi (Mn-PANi) composite, which was found to be 633.75 Fg−1.

Reduced graphene oxide/molybdenum oxide thin films and its’ capacitance properties: Different substrates effect

This study used the Chemical Bath Deposition method, which is quite simple and cheap, to produce GO/MoO3 nanocomposite, whose high capacitance properties draws attention. The Graphene oxide solution is prepared by synthesizing through the Hummer Method. These two materials were left to grow slowly on their own so that GO/MoO3 nanocomposite structures form thin films on Glass, Poly(methyl methacrylate), Fluorine tin oxide, and indium tin oxide substrates. The surface and structural properties of these GO/MoO3 nanocomposite structures were characterized by Scanning Electron Microscopy, Energy Dispersive X-ray, FTIR, X-ray diffraction, and Atomic Force Microscopy. The nanocomposites' capacitance properties produced on different substrates were measured in -0.2 – 0.2 V at different scan rates. As a result, the highest specific capacitance values were achieved at 25 mV/s scan rate, as 587 F/g, for Poly(methyl methacrylate).

Pencil peel derived mixed phase activated carbon and metal-organic framework derived cobalt-tungsten oxide for high-performance hybrid supercapacitors

In this work, pencil peel is used to derive the mix phase activated carbon at different temperatures viz 700, 800, and 900 °C for hybrid supercapacitor applications. The derived carbon is showing the highest specific surface area for P-800 (Pencil peel@ 800 °C) sample and exhibits the graphitic and amorphous phase whose fraction can be controlled with pyrolysis temperature. Therefore, the as-prepared P-800 electrode shows the high specific capacitance of 553 F/g at a current density of 1 A/g. On the other hand, metal-organic framework (MOF) derived Cobalt-Tungsten oxide composites (Co3O4/WO3) has been synthesized which shows a much higher specific capacitance value (544 F/g at 2 A/g) in the negative potential window. Therefore, an asymmetrical supercapacitor device has been assembled with P-800 as positive and Co3O4/WO3 composites as a negative electrode in aqueous 1 M H2SO4 (Sulfuric acid) electrolyte that delivers higher energy and power density in comparison to their symmetrical supercapacitor counterparts.

Chalcogenide Dopant-Induced Lattice Expansion in Cobalt Vanadium Oxide Nanosheets for Enhanced Supercapacitor Performance

We explore the effect of sulfur doping in Co3V2O8 on the electrochemical performance of supercapacitors in terms of enhanced lattice spacing, electrochemical surface area (ECSA), electronic conductivity, and density of states. The sulfur-doped Co3V2O8 (S-Co3V2O8) nanosheets were grown in situ as a binder-free synthesis on nickel foam by the hydrothermal method. The electrochemical performance was analyzed in an aqueous alkaline electrolyte where the S-Co3V2O8 electrode exhibited a specific capacity of 410 mAh/g at 2 A/g with enhanced rate capability and capacity retention of 94.2% at 5 A/g specific currents after 4000 cycles, whereas the undoped Co3V2O8 electrode exhibited a specific capacity of 337.8 mAh/g at 2 A/g. The high capacity of S-Co3V2O8 is attributed to the enhanced ECSA (by ∼45%) and improved electrical conductivity (by ∼22%) upon doping with sulfur. Furthermore, these results corroborated with density functional theory results. The calculations suggest an increase in lattice parameters and the introduction of additional density of states near the valence-band edge due to the doping of sulfur, resulting in a decrease in charge-transfer resistance. An asymmetric supercapacitor was fabricated, using S-Co3V2O8 nanosheets as the cathode and activated carbon as the anode, which shows a high specific capacity (or capacitance) value of 485 mAh/g, an energy density of 36.4 W h/kg, and a power density of 740 W/kg at 2 A/g with 98.4% specific capacity retention after 4000 consecutive charge–discharge cycles. Furthermore, the analysis was extended in a nonaqueous medium for Li-ion storage where S-Co3V2O8 exhibits a specific capacity of 994 mA h/g and a specific energy density of 828 W h/kg at 1 A/g making it a promising candidate for future high-energy storage systems. The concept of doping is extended to other chalcogenide (e.g., selenium) doping (Se-Co3V2O8), which also shows improved device performance and makes this a versatile approach for high-performance devices.

Ice-colloidal templated carbon host for highly efficient, dendrite free Li metal anode

With its high theoretical specific capacity value, lithium metal itself would be an ideal anode material for rechargeable Li-ion batteries (LIBs). However, practical application of lithium metal is obstructed due to lithium dendrite growth during cycling leads to unstable SEI formation, volume fluctuation and safety hazard. Herein, we have developed a novel high surface area carbon network with both meso (∼20 nm) and micron (∼1–2 μm) size porosity, via ice-colloidal templating, as a scaffold for stable lithium metal anode mitigating lithium dendrite formation. The 3D porous nitrogen doped carbon (3D PNC) network is capable of lithium deposition equivalent to 10 mAhcm−2 at 2 mAcm−2 current density with 99.96% coulombic efficiency for 100 cycles. Moreover, 3D PNC when subjected to 3000 h of continuous plating-stripping measurements (∼700 cycles) depicts the coulombic efficiency of 99.84% with no observable dendrite growth at the current density of 2 mAcm−2 and lithium intake capacity of 5 mAhcm−2. A full cell of lithium plated 3D PNC anode with LiFePO4 shows an excellently stable performance up to 50 cycles at an input current density of 50 mAg−1, with a coulombic efficiency retention of 99.73%.

A novel binder free high performance Y2Zr2O7/MnS nanocomposite electrode for supercapacitor applications

Metal oxides and sulfides nanocomposites with mesoporous structure are gaining attention in the field of supercapacitors owing to their high surface area and appropriate pore size distribution. Such nanocomposites deliver high values of specific capacitance due to effective contacts between the electrode and the electrolytes. Moreover, the high value of the specific capacitance is attributed to fast transport of ions and electrons in the bulk and at the interface of the electrode and the electrolyte. The present study reports synthesis and the fabrication of a high-performance electrode consisting of Y2Zr2O7/MnS nanocomposite as a dynamic material for supercapacitor application. Because of distinctive morphology, the unique electrode consisting of Y2Zr2O7/MnS nanocomposite can store and tolerate a specific capacitance of 262 F/g at a potential window of 0.75 V. The nanocomposite electrode demonstrates a high cyclic stability over 4500 successive cycles of cyclic voltammetry (CV). The specific capacitance increases from 145 to 905 F/g after successive 4000 CV cycles. The ability to tolerate high specific capacitance, withstanding over successive CV cycles and its outperformance suggests that Y2Zr2O7/MnS nanocomposite can be an alternative high performance electrode for next generation supercapacitors.

Sea urchin-shaped Fe2O3 coupled with 2D MXene nanosheets as negative electrode for high-performance asymmetric supercapacitors

Fe2O3 is one of promising negative materials for supercapacitors (SCs), because of its low cost and high theoretical value of specific capacitance. However, the inferior conductivity and insufficient ionic diffusion rate of Fe2O3 will seriously hinder the electrochemical performance of Fe2O3, resulting in limiting its practical application in SCs. Herein, a sea urchin-like 3D Fe2O3 was synthesized via hydrothermal methods. And then, the 2D Ti2C3Tx MXene nanosheets with high conductivity closely self-assemble on the surface of Fe2O3 to provide efficient pathways for the rapid electrons transport. In addition, the sea urchin-like structure of Fe2O3 can facilitate the rapid diffusion of the electrolyte to accelerate faradaic reaction. The optimized Fe2O3/MXene composite as electrode material exhibits a high specific capacitance of 486.3 F g−1 at current density of 1 A g−1, and excellent cycling stability with 95.7% capacity retention after 5000 charge/discharge cycles. Furthermore, an asymmetric supercapacitors (ASCs) device was assembled by using Fe2O3/MXene composite as anode and MnO2 as cathode, showing a high energy density of 32.2 Wh kg−1 at the power density of 900.6 W kg−1, and remarkable long-term durability (95.7 % capacitance retention after 5000 cycles). This work demonstrates an effective approach of integrating the sea urchin-like Fe2O3 with 2D MXene nanosheets to fabricate Fe2O3/MXene composite for high-performance SCs.

Specific Heat Capacity Estimations for Biologically and Medicinally Important Compounds: Lidocaine Hydrochloride, Clove Oil and β-Piperine Using the DSC Technique

Aim: To study the specific heat capacity for biologically and medicinally important compounds, namely, lidocaine hydrochloride, clove oil and beta-Piperine using the DSC technique. Background: One of the main problems in the science of medicine is the application of drug molecules with limited solubility in water and in biofluids. Solubility is related to the chemical potential of the solutes involved, which imparts free energy avenues, a necessary requirement for equilibrium processes. The convincing solutions for solving this issue are the utilization of ionic liquids as a drug. Lidocaine is the most widely utilized intraoral injected dental anesthetic prior to performing painful medical procedures. Besides that, lidocaine hydrochloride is a salt, having a melting point of 76°C (349 K) and behaves as an ionic liquid after melting. Clove oil and β-piperine are very well-known naturally occurring medicinal compounds having a broad spectrum of applications. Objective: To study the thermal gravimetry analysis behaviour for lidocaine hydrochloride, clove oil and β-piperine. To compute specific heat capacity at constant pressure, as a function of temperature for the studied systems. Methods: In the present communication, the studies of Thermal Gravimetry Analysis (TGA) and Differential Scanning Calorimetry (DSC) for these compounds are described. Results: The data of heat flow have been utilized to obtain specific heat capacity (Cp) values for lidocaine hydrochloride, clove oil and β-piperine over a temperature range between 75°C (348 K) and 155°C (428 K) based upon the methodology we have developed. Conclusion: LC•HCl behaves as an ionic liquid between 76 and 230°C (349 and 503 K). Clove oil shows lower specific heat capacity values and is similar to other organic aromatic compounds while piperine exhibits comparative high specific heat capacity values indicating possibilities of intramolecular hydrogen bonding, which is generally not affected by temperature.

Controlled chemical oxidative polymerization of conductive polyaniline with excellent pseudocapacitive properties

Nowadays, the application of supercapacitor in energy storage is more and more extensive, and the selection and preparation of electrode material have become a formidable challenge. Polyaniline (PANI) has turned into one of the most hopeful conductive polymers due to its superior properties. In this article, conductive polyaniline was synthesized by chemical oxidative polymerization to acquire excellent electrochemical properties. Scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD) measurements were adopted to explore the microstructure and energy storage capacity. The PANI is in coralline network morphology with high surface area, which can supply more active sites during charge and discharge process. The PANI shows a high specific capacitance value of 790 F/g, and the highest conductivity is 15.5 S/cm. The consequence shows that PANI synthesized under certain conditions has a promising feasibility for applications in high-performance supercapacitor electrode material.

Asymmetric micro-supercapacitors based on electrodeposited Ruo2 and sputtered VN films

Research on micro-supercapacitors remains one of the most important activities in the area of electrochemical energy storage for powering smart and miniaturized electronic devices. Here we design an asymmetric micro-supercapacitor (A-MSC) combining sputtered vanadium nitride film (VN) and electrodeposited hydrous ruthenium oxide (hRuO2) film. Taking advantage of their complementary electrochemical potential windows in 1 M KOH electrolyte, the A-MSC achieves a cell voltage up to 1.15 V, associated to high specific capacitance values for the device (≈ 100 mF cm−2). The energy density of this asymmetric VN / hRuO2 micro-supercapacitor reaches 20 µWh cm−2 at a power density of 3 mW cm−2. Taking benefit from the asymmetric configuration, a 5-fold enhancement factor in energy density is demonstrated for the VN / hRuO2 asymmetric micro-supercapacitor as compared to symmetric VN / VN and hRuO2 / hRuO2 microdevices.

Design and synthesis of polyaniline/MWCNT composite hydrogel as a binder-free flexible supercapacitor electrode

The novel polyaniline/MWCNT composite hydrogel has been successfully synthesized on carbon cloth using in situ oxidative polymerization of aniline in the presence of MWCNT and phytic acid which can further be used as a binder-free electrode for supercapacitor. The use of electrode without binder is an effective approach to get better electrochemical behavior, which makes the ions move quicker. The supercapacitor cell has been built in a Teflon Swagelok assembly by sandwiching a separator impregnated with 1 M H2SO4 electrolyte between two symmetrical hydrogel electrodes and used further for electrochemical characterization. The electrochemical behavior of supercapacitor electrodes has been explored in a two-electrode cell configuration using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements. The electrochemical results reveal that in 1 M H2SO4 aqueous solution, polyaniline/MWCNT composite hydrogel possesses a high specific capacitance (Cs) value of 277.59 F/g as compared to Cs value of 142.24 F/g for polyaniline hydrogel at 0.25 A/g. The polyaniline/MWCNT electrode shows superior rate capability and outstanding cyclic stability up to 5000 consecutive cycles. The electrochemical performance of composite hydrogel may be attributed to its well-designed nanostructure and the collective effect of both components. It may be concluded that as prepared composite hydrogel serves as a favorable electrode material for highly capable flexible energy storage system.