Fabrication Of Supercapacitor Electrodes Research Articles

Application of Rhamnolipids as Dispersing Agents for the Fabrication of Composite MnO2-Carbon Nanotube Electrodes for Supercapacitors.

The high theoretical capacitance of MnO2 renders it a promising material for the cathodes of asymmetric supercapacitors. The good dispersion of MnO2 and conductive additives in a nanocomposite electrode is a key factor for efficient electrode performance. This article describes, for the first time, the application of rhamnolipids (RL) as efficient natural biosurfactants for the fabrication of nanocomposite MnO2-carbon nanotube electrodes for supercapacitors. RL act as co-dispersants for MnO2 and carbon nanotubes and facilitate their efficient mixing, which allows for advanced capacitive properties at an active mass of 40 mg cm−2 in Na2SO4 electrolytes. The highest capacitance obtained from the cyclic voltammetry data at a scan rate of 2 mV s−1 is 8.10 F cm−2 (202.6 F g−1). The highest capacitance obtained from the galvanostatic charge–discharge data at a current density of 3 mA cm−2 is 8.65 F cm−2 (216.16 F g−1). The obtained capacitances are higher than the capacitances of MnO2-based electrodes of the same active mass reported in the literature. The approach developed in this investigation is simple compared to other techniques used for the fabrication of electrodes with high active mass. It offers advantages of using a biocompatible RL biosurfactant.

Facile Route for Fabrication of Ferrimagnetic Mn3O4 Spinel Material for Supercapacitors with Enhanced Capacitance

The purpose of this investigation was the development of a new colloidal route for the fabrication of Mn3O4 electrodes for supercapacitors with enhanced charge storage performance. Mn3O4-carbon nanotube electrodes were fabricated with record-high capacitances of 6.67 F cm−2 obtained from cyclic voltammetry tests at a scan rate of 2 mV s−1 and 7.55 F cm−2 obtained from the galvanostatic charge–discharge tests at a current density of 3 mA cm−2 in 0.5 M Na2SO4 electrolyte in a potential window of 0.9 V. The approach involves the use of murexide as a capping agent for the synthesis of Mn3O4 and a co-dispersant for Mn3O4 and carbon nanotubes. Good electrochemical performance of the electrode material was achieved at a high active mass loading of 40 mg cm−2 and was linked to a reduced agglomeration of Mn3O4 nanoparticles and efficient co-dispersion of Mn3O4 with carbon nanotubes. The mechanisms of murexide adsorption on Mn3O4 and carbon nanotube are discussed. With the proposed method, the time-consuming electrode activation procedure for Mn3O4 electrodes can be avoided. The approach developed in this investigation paves the way for the fabrication of advanced cathodes for asymmetric supercapacitors and multifunctional devices, combining capacitive, magnetic, and other functional properties.

Supercapacitor electrode fabrication through chemical and physical routes

In recent years, efficient energy storage devices that exhibit superior power and energy densities have attracted major attention to meet the demands of emerging applications such as wearable systems. In this regard, supercapacitors (SCs) in various forms offer attractive solutions. The performance of SCs is highly dependent on the synthesis route used for electrode materials preparation. This review outlines various techniques for electrode materials fabrication, such as i) solution-based chemical techniques, ii) physical methods, and iii) deposition techniques. Accordingly, different solution-based procedures such as hydrothermal/solvothermal, sol-gel, microwave, and in-situ polymerization techniques offer facile and cost-effective routes to synthesise electrode materials. Physical deposition techniques such as vacuum filtration and mechanochemical methods are also explained. The scalability to develop flexible structures is an attractive feature of physical approaches. Chemical vapour deposition, electro-polymerization/electrochemical deposition and direct growth techniques are also discussed in detail. It is suggested that incorporating electrode materials with 3D conductive substrate and hierarchical structures minimizes the excessive mass loading in commercial scale-up of SCs. Supercapacitor electrodes with shape memory properties for developing smart textiles are also presented. It is concluded that incorporating more than one synthetic approach makes it possible to obtain the electrode material for excellent electrochemical properties.

Binder-free CoMn2O4/carbon nanotubes composite electrodes for high-performance asymmetric supercapacitor

This study presents the fabrication of supercapacitor electrodes composed of CoMn2O4 (CMO) nanosheets coated onto carbon nanotubes which are grown on a stainless-steel mesh (SSM). The synthesis includes chemical vapor deposition of carbon nanotubes (CNTs) on the SSM followed by annealing at 450 °C in air for 2 h in order to generate defects for further electrodeposition of CMO nanosheets. The electrodeposited CMO exhibits excellent pseudocapacitive performance owing to high oxidation potential of cobalt as well as the fast electron transportation ability of manganese. By controlling the deposition time of CMO, favorable morphology and excellent capacitance can be achieved. Furthermore, the direct growth of CMO on CNTs/SSM prevents the use of binders or additives and avoids undesired resistances. The binder-free CMO/CNT electrode exhibits a superior specific capacitance of 732 F/g at a scan rate of 2 mV/s. Furthermore, an asymmetric supercapacitor was fabricated by paring the CMO/CNT electrode with activated carbon as an anode. The asymmetric supercapacitor exhibits an energy density of 47.39 W/kg with a power density of 400 Wh/kg together with good stability of 77% capacitance retention after 5000 cycles, which suggest that the composite electrode is of great significance for practical energy storage devices.

Fabrication of supercapacitor electrode based on pepper peel activated carbon

Pepper peel waste is one of the byproducts of pepper production, especially in the Province of Bangka Belitung Islands. One of the efforts to utilize pepper peel, which is used as an activated carbon material that can be used as supercapacitor electrodes, has been carried out. Activated carbon based on pepper peel is synthesized by drying it to dry and then pre-carbonization. The next step is chemical activation using ZnCl2 and followed by physical activation at 700 °C in nitrogen flow conditions (N2) for 3 hours. Characterization of activated carbon material was carried out using SEM-EDX and BET, while the electrode performance used CV (Cyclic Voltamettry). The SEM-EDX and BET test results show that the activated carbon material has a porous structure with an average pore diameter of 2.059 nm. The CV test results were used to determine the energy storage capability with a specific capacitance value of 7.77 F/g at a scan rate of 1 mV/s.

Excellent supercapacitive performance of graphene quantum dots derived from a bio-waste marigold flower (Tagetes erecta)

Marigold flower (MG; Tagetes erecta) derived Graphene quantum dots (GQDs) have been successfully reported for the fabrication of supercapacitor electrodes in charge storage devices. The GQDs have been synthesized through a hydrothermal route using biomass viz. Waste material (MG) without adding any hazardous chemicals. The successful formation of GQDs as elaborated has been confirmed by various analytical characterization techniques. The as-synthesized GQDs have been electrodeposited on the Ni foil (working electrode) with the help of PVDF (binder) and subsequently, cyclic voltammetry (CV) has been conducted to access specific capacitance, energy density, and other parameters. Moreover, the galvanometric charge/discharge (GCD) technique has been employed due to its accuracy and reliability. Maximum areal specific capacitance has been found as 1.6008 F/cm2 with the current density of 2.0 A/g even after loading a little amount of material on the electrode. The high magnitude of columbic efficiency (160.08), energy density (17.78 Wh/kg), and specific capacitance of 200 F/g at current density 2.0 A/g within a voltage range of −0.55 V to +0.25 V in 2 M KOH electrolyte solution indicate a good electrocapacitive performance of the as-synthesized material. Moreover, the as-synthesized GQDs have shown excellent capacitive retention after 1000th cycles which clearly embarks its sustainable electrocapacitive nature and henceforth offers outstanding potential for the applications in energy storage devices like supercapacitors.

Fabrication of Multilayered Composite Nanofibers Using Continuous Chaotic Printing and Electrospinning: Chaotic Electrospinning.

Multi-material and multilayered micro- and nanostructures are prominently featured in nature and engineering and are recognized by their remarkable properties. Unfortunately, the fabrication of micro- and nanostructured materials through conventional processes is challenging and costly. Herein, we introduce a high-throughput, continuous, and versatile strategy for the fabrication of polymer fibers with complex multilayered nanostructures. Chaotic electrospinning (ChE) is based on the coupling of continuous chaotic printing (CCP) and electrospinning, which produces fibers with an internal multi-material microstructure. When a CCP printhead is used as an electrospinning nozzle, the diameter of the fibers is further scaled down by 3 orders of magnitude while preserving their internal structure. ChE enables the use of various polymer inks for the creation of nanofibers with a customizable number of internal nanolayers. Our results showcase the versatility and tunability of ChE to fabricate multilayered structures at the nanoscale at high throughput. We apply ChE to the synthesis of unique carbon textile electrodes composed of nanofibers with striations carved into their surface at regular intervals. These striated carbon electrodes with high surface areas exhibit 3- to 4-fold increases in specific capacitance compared to regular carbon nanofibers; ChE holds great promise for the cost-effective fabrication of electrodes for supercapacitors and other applications.

A simple procedure for fabricating graphene or modified graphene polyaniline composites for supercapacitor application

The depleting fuel resources and elevated air pollution are raising serious concerns among the global population. The fuel prices are also increasing day by day. Hence the world is more focused on maximizing conventional energy resources like solar, tidal, wind energies, etc. However, for the fullest utilization of conventional energy sources, we need efficient energy storage systems, and currently, we are using batteries as the primary energy storage elements. Nowadays, researchers are giving utmost importance to the development of supercapacitors. Graphene coming under carbon groups and polyaniline (PANI), coming under electronic conducting polymers (ECP), are two different materials mainly used for supercapacitor electrode fabrication. The normal route for synthesizing graphene-PANI composites is a time-consuming process. Here we present a simple route for synthesizing graphene-PANI composites. The same method can be adopted for fabricating modified graphene-PANI composites too. The FTIR, Raman spectroscopy, XRD, SEM, and TEM results showed that the formation of graphene-PANI composites in the current route is the same as that of the normal method. Moreover, the cyclic voltammetry (CV) and charge–discharge (CD) tests revealed excellent electrochemical performance and cyclability. The CV study reported that the specific capacitances of the supercapacitor are 235, 179, 120, 85, and 55 F/g at scan rates of 10, 20, 50, 100, and 200 mV/s.The capacitance retention ratio was more than 90% and the ESR was found to be 10.5 O.

Investigation of hard/soft CoFe 2 O 4 / NiSc 0 . 03 Fe 1 . 97 O 4 nanocomposite for energy storage applications

The hard/soft CoFe2O4/(NiSc0.03Fe1.97O4)x (0 ≤ x ≤ 5) or simply (CFO-xNFSO) nanocrystals (NCs) were synthesized through sol–gel auto-combustion technique. The structural and magnetic properties of the ferrite composite NCs were explored in detail. The synthesized NCs were applied in the fabrication of supercapacitor electrodes to investigate their potential in energy storage applications. The cubic spinel ferrite phase of the NCs was verified by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM) techniques. The NCs with different x ratios displayed smoothed magnetic hysteresis loops during magnetization at 300 and 10 K temperature. In addition, the plots of switching field distribution (SFD) indicated a single peak in dM/dH vs H plots. These findings demonstrate a good exchange-coupling in the CFO-xNFSO (0.0 ≤ x ≤ 5) magnetic NCs. The supercapacitor devices fabricated from the synthesized NCs displayed enhanced capacitance and relatively high energy density as compare to electric double-layer (EDL) (carbon-based) supercapacitors. The supercapacitor fabricated from CFO-xNFSO for x = 2 showed best performance in terms of specific capacitance with 204.4 F g−1 at a scan rate of 10 mV s−1. The performances of the fabricated supercapacitors were further tested for a higher potential window of 1.2 V, where a specific energy value of 33.2 Wh kg−1 is achieved that is 144% enhancement from the same supercapacitor working at 0.8 V and 187% enhancement as compared to the carbon-based supercapacitor. The device also displayed excellent stability as it was tested for 5000 charge–discharge cycles.

DFT computation of quantum capacitance of pure and doped niobium nitrides for supercapacitor applications

The density of states and quantum capacitance of pure and doped niobium nitrides are investigated using density functional theory calculations. Out of pristine structures investigated, NbN is the most promising candidate for fabrication of supercapacitor electrodes with quantum capacitance values reaching up to 834.5 and 1683.7 Fg-1 at negative and positive electrodes respectively. These calculations are also performed for cobalt doped niobium nitrides. The results suggest that doping of niobium nitrides with cobalt can further increase the quantum capacitance significantly. Quantum capacitance of both pristine and doped niobium nitrides is found to be much higher than that of graphene near fermi level, thus suggesting that these structures can be preferred over graphene for supercapacitor electrodes. The temperature dependence of quantum capacitance is also investigated.

Lignin-based electrodes for energy storage application

As the second most abundant organic polymers in nature, lignin demonstrates advantages of low cost, high carbon content, plentiful functional groups. In recent years, lignin and its derivatives, as well as lignin-derived porous carbon have emerged as promising electrode materials for energy storage application. In this review, recent progress on the design and fabrication of lignin-based electrode materials for energy storage application is summarized. We begin with a brief summary of the separation process and basic chemistry of lignin. Then, the latest development on the fabrication of lignin-based electrodes for supercapacitors and batteries is elaborated separately. Finally, we propose the current challenges and future prospects of the lignin-based electrodes for advanced energy storage devices.

Application of Octanohydroxamic Acid for Salting out Liquid-Liquid Extraction of Materials for Energy Storage in Supercapacitors.

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.

Reduced Graphene Oxide Composited with Ni-MOF and PANI Applied as Electrodes for Supercapacitor

The different composites made of rGO, Ni-MOF, and PANI were synthesized via the hydrothermal method and used for the fabrication of electrodes for supercapacitors. The structure and morphology of composites obtained were characterized via SEM, XRD, and FTIR. The electrochemical properties of electrodes were studied using CV and galvanostatic charge/discharge methods, as well as by EIS. The results obtained demonstrated that the incorporation of rGO, Ni-MOF, and PANI significantly increase the specific capacitance of electrodes. It can be explained by the formation of a better specific surface area with a branched porous structure that enhances the contact between electrolyte ions with the electrode materials. The specific capacitance of rGO/Ni-MOF/PANI in 1 M H2SO4 electrolyte is 195.14 F/g at 0.2 A/g charge-discharge and the average capacitance retention remained 79.78% after 5,000 cycles at current density 1 A/g.

Inherent Impurities in Graphene/Polylactic Acid Filament Strongly Influence on the Capacitive Performance of 3D-Printed Electrode.

Additive manufacturing or 3D-printing have become promising fabrication techniques in the field of electrochemical energy storage applications such as supercapacitors, and batteries. Of late, a commercially available graphene/polylactic acid (PLA) filament has been commonly used for Fused Deposition Modeling (FDM) 3D-printing in the fabrication of electrodes for supercapacitors and Li-ion batteries. This graphene/PLA filament contains metal-based impurities such as titanium oxide and iron oxide. In this study, we show a strong influence of inherent impurities in the graphene/PLA filament for supercapacitor applications. A 3D-printed electrode is prepared and subsequently thermally activated for electrochemical measurement. A deep insight has been taken to look into the pseudocapacitive contribution from the metal-based impurities which significantly enhanced the overall capacitance of the 3D-printed graphene/PLA electrode. A systematic approach has been shown to remove the impurities from the printed electrodes. This has a broad implication on the interpretation of the capacitance of 3D-printed composites.

High- performance aqueous electrolyte based supercapacitor of carboxylic acid functionalized carbon-nanotubes and graphene nano composite

High specific capacitance of supercapacitors is the most prominent factor for its implementation in industrial use. However various methods has been employed to intensify the specific capacitance of supercapacitors by fabricating electrodes using graphene composite as active electrode material. However those methods have been able to attain the desired specific capacitance of the supercapacitors but there still remains some disadvantageous factors that act as hurdles for their implementation in practical field. In this work the synthesis and supercapacitor electrode fabrication of carboxylic acid functionalized carbon nanotubes/graphene composite (rGO/FCNT) has been reported without destroying the 2D sheets structures of reduced graphene oxide sheets. The carboxylic functionalities were introduced into the surface of the carbon nanotubes by treatment with H2SO4/HNO3 mixture. The final composites were synthesized by in-situ reduction of graphene oxide (GO) in presence of functionalized carbon nanotubes by the addition of hydrazine hydrate. Supercapacitor electrodes were fabricated using these composites where stainless steel plates of 1 cm2 area were used as current collectors. The materials were characterized by FTIR, Raman Spectroscopy, Scanning Electron Microscopy (SEM), X-ray photo electron spectroscopy (XPS) and XRD analysis. The surface area of the composite was determined by BET isotherm analysis. The electrochemical properties of the electrodes were evaluated by cyclic voltammetry (CV), galvenostatic charge discharge study and impedance spectroscopy. The material shows a specific capacitance of 302 F/g at a current density of 1 A/g. The newly prepared composite hold an optimistic potential to be used as electrode material in energy storage devices. The inter planer distance between the graphene nanosheets and the nature of interaction between graphene and functionalized carbon nanotubes were theoretically studied by Density Functional Theory (DFT) study.

Sustainable synthesis of organic framework-derived ZnO nanoparticles for fabrication of supercapacitor electrode

ABSTRACT The phytosynthesis of metal oxides nanoparticles (NPs) has been extensively reported; yet mechanism involved and incorporated bioactive compounds in the synthesized NPs are still need to be investigated. In this regard, here an efficient sustainable co-precipitation synthesis of zinc oxide nanoparticles (ZnO NPs) has been developed, employing hydrothermal reactions, using organic compounds of Nasturtium officinale leaves. Pure hexagonal wurtzite ZnO was identified by X-ray diffraction and NPs in the size range of 50–60 nm were observed by field emission scanning electron microscopy. X-ray photoelectron spectroscopy revealed surface modification of ZnO by functional groups associated with the incorporated bio active compounds of Nasturtium officinale. The phyto-functionalized ZnO NPs having anoptical direct band gap of 3.29 eV and optical band gap energy of 2.85 eV were evaluated by cyclic voltammetry at various scan rates, galvanostatic charge–discharge at a range of current densities and electrochemical impedance spectroscopy (Z′ vs. Z″ and Z vs. frequency) in aqueous electrolyte. The fabricated ZnO-based electrode revealed a specific capacitance of 86.5 F/g at 2 mV/s with 97% coulombic efficiency for 2000 cycles. The good electrochemical conductivity was demonstrated by lower internal resistance of 1.04 Ω. Therefore, the present study suggested the significant potential of organic compounds incorporated ZnO NPs towards supercapacitor.

Cost‐Effective Synthesis of Electrodeposited NiCo2O4 Nanosheets with Induced Oxygen Vacancies: A Highly Efficient Electrode Material for Hybrid Supercapacitors

AbstractNanostructured transition metal oxide synthesis possessing high energy density and stability is desirable for supercapacitors. Herein, we synthesize three‐dimensional NiCo2O4 (NCO) nanosheets with oxygen vacancies induced by sustainable and environmentally benign electrodeposition assisted chemical reduction process. Oxygen vacancies increase the conductivity, adsorptivity, and the active surface area, thereby enhancing the charge storage capabilities. The binder‐free NCO delivers the highest specific capacitance (Csp) of 2065 F g−1 at 1 A g−1, retaining 89.30 % of its initial value at 10 A g−1 after 10,000 continuous charge‐discharge (CD) cycles. An asymmetric supercapacitor (ASC) fabricated shows remarkable electrochemical properties with high energy density (Emax) of 28.6 Wh kg−1 and power density (Pmax) of 7.5 kW kg−1. The assembled ASC reports exceptional cyclic retention of 90.6 % for 10,000 CD cycles with practical demonstration. The approach used herein is suitable for eco‐friendly supercapacitor electrode fabrication with large scale manufacturing capability and less capital investment.

Flexible Type Symmetric Supercapacitor Electrode Fabrication Using Phosphoric Acid-Activated Carbon Nanomaterials Derived from Cow Dung for Renewable Energy Applications.

Porous-activated carbon (PAC) materials have been playing a vital role in meeting the challenges of the ever-increasing demand for alternative clean and sustainable energy technologies. In the present scenario, a facile approach is suggested to produce hierarchical PAC at different activation temperatures in the range of 600 to 900 °C by using cow dung (CD) waste as a precursor, and H3PO4 is adopted as the nonconventional activating agent to obtain large surface area values. The as-prepared cow dung-based PAC (CDPAC) is graphitic in nature with mixed micro- and mesoporous textures. High-resolution scanning electron microscopy depicts the morphology of CDPAC as nanoporous structures with a uniform arrangement. High-resolution transmission electron microscopy reveals spherical carbon dense nanoparticles with dense tiny spherical carbon particles. N2 adsorption–desorption isotherms show a very high specific surface area of 2457 m2/g for the CDPAC 9 (CD 9) sample with a large pore volume of 1.965 cm3/g. Electrochemical measurements of the CD 9 sample show a good specific capacitance (Cs) of 347 F/g at a lower scan rate (5 mV/s) with improved cyclic stability, which is run up to 5000 cycles at a low current density (0.5 A/g). Hence, we choose an activated carbon prepared at 900 °C to fabricate the modified electrode material. In this regard, a flexible type symmetric supercapacitor device was fabricated, and the electrochemical test results show a supercapacitance value (Cs) of 208 F/g.

Fabrication and electrochemical characterization of graphene-oxide supercapacitor electrodes with activated carbon current collectors on graphite substrates

Electrochemical energy storage plays a major rule in the current shift to renewable energy sources in the form of batteries, supercapacitors, and fuel cells. This work represents the fabrication of supercapacitor electrodes comprised of activated carbon powder (ACP) and graphene oxide (GOx) drop-casted onto graphite substrates. ACP, based on its performance in a beaker cell in aqueous 1M H2SO4, was used as a current collector to enhanced the performance of the GOx electrodes. A graphitic device fabricated with ACP/GOx layered electrodes produced a specific capacitance of 16.5 F/g and energy density of 2.3 Wh/kg at scan rate of 10 mV/s.

Pinecone biomass‐derived activated carbon: the potential electrode material for the development of symmetric and asymmetric supercapacitors

Activated carbon, from biomass (pinecone), was synthesized by conventional pyrolysis/chemical activation process and utilized for the fabrication of supercapacitor electrodes. The pinecone-activated carbon synthesized with 1:4 ratio of KOH (PAC4) showed an increase in surface area and pore density with a considerable amount of oxygen functionalities on the surface. Moreover, PAC4, as supercapacitor electrode, exhibited excellent electrochemical performances with specific capacitance value ∼185 Fg−1 in 1 M H2SO4, which is higher than that of nonactivated pinecone carbon and 1:2 ratio KOH-based activated carbon (PAC2) (∼144 Fg−1). The systematic studies were performed to design various forms of devices (symmetric and asymmetric) to investigate the effect of device architecture and operating voltage on the performance and stability of the supercapacitors. The symmetric supercapacitor, designed utilizing PAC4 in H2SO4 electrolyte, exhibited a maximum device-specific capacitance of 43 Fg−1 with comparable specific energy/power and excellent stability (∼96% after 10 000 cycles). Moreover, a symmetric supercapacitor was specially designed using PAC4, as a positive electrode, and PAC2, as a negative electrode, under their electrolytic ion affinity, and which operates in aqueous Na2SO4 electrolyte for a wide cell voltage (1.8 V) and showed excellent supercapacitance performances. Also, a device was assembled with poly(3,4-ethylene dioxythiophene) (PEDOT) nanostructure, as positive electrode, and PAC4, as a negative electrode, to evaluate the feasibility of designing a hybrid supercapacitor, using polymeric nanostructure, as an electrode material along with biomass-activated carbon electrode.