Active Material For Supercapacitors Research Articles

Investigation of characteristics of double Ni–Co and ternary Ni–Co–Al layered hydroxides for supercapacitor application

Nickel hydroxides are widely used as the active material in supercapacitors. To improvise electrochemical activity, activators, namely Co and Al compounds, are introduced into the structure of nickel hydroxide. The most effective is the introduction of activators directly into the structure of nickel hydroxide. Characteristics of double Ni–Co (Ni:Co=8:1) and triple Ni–Co–Al (Ni:Co:Al=8:1:2) hydroxides, synthesized by single-stage reverse titration method were studied. Crystal structure of the samples was studied by means of X-ray diffraction analysis, thermogravimetry and differential scanning calorimetry, electrochemical characteristics were studied by means of cyclic voltammetry and galvanostatic charge-discharge cyclic in supercapacitor regime. Comparative analysis of characteristics of double Ni–Co and triple Ni–Co–Al hydroxide was conducted. By means of XRD analysis, thermogravimetry, and differential scanning calorimetry it was found that Ni–Co–Al is layered triple hydroxide with the structure of α-Ni(OH) 2 with high crystallinity. Ni-Co hydroxide is double Ni–Co hydroxide with the crystal lattice of β-Ni(OH) 2 , in which part of Ni 2+ is isostructurally substituted by Co 2+ , and low crystallinity. By means of cyclic voltammetry and galvanostatic charge-discharge cycling, high electrochemical activity of Ni–Co hydroxide was found. By means of cyclic voltammetry, an abnormal, α-like behavior of Ni–Co with β-Ni(OH) 2 lattice was found . The electrochemical activity of triple Ni–Co–Al hydroxide was found to be significantly lower than that of double Ni–Co hydroxide (maximum specific capacities are 550.4 F/g and 741.5 F/g, respectively), despite the structure of pure layered double hydroxide and presence of two activators. A hypothesis was proposed on the poisoning of Ni–Co–Al LTH with free aluminum compounds during reverse titration synthesis

Scalable one-pot synthesis of bismuth sulfide nanorods as an electrode active material for energy storage applications

The quest for developing the scalable methods of synthesis of materials with potential electrochemical energy storage applications remains a great challenge. Herein, we propose a facile, one-step chemical precipitation method for the synthesis of Bi2S3 with the nanorods morphology. Influence of different synthesis temperatures on the physical, chemical, and electrochemical performance was investigated. Relatively low BET surface area and mesopore volume of Bi2S3 increased with the higher reaction temperature. Bismuth sulfides synthesized at various temperatures were used as an electrode active material in supercapacitor. The semiconductive properties of Bi2S3 resulted in exceptional capacitive behavior. Bismuth sulfide synthesized at 75 °C exhibited a specific capacitance of 457 F g−1 at 1 A g−1 in 6 mol L−1 KOH solution as an electrolyte. Moreover, material prepared at 75 °C maintained the best capacitance value at a large current density of 20 A g−1, compared with bismuth sulfides synthesized at the temperatures of 0 °C and 25 °C.

Supercapacitors on demand: all-printed energy storage devices with adaptable design

Demands on the storage of energy have increased for many reasons, in part driven by household photovoltaics, electric grid balancing, along with portable and wearable electronics. These are fast-growing and differentiated applications that need large volume and/or highly distributed electrical energy storage, which then requires environmentally friendly, scalable and flexible materials and manufacturing techniques. However, the limitations on current inorganic technologies have driven research efforts to explore organic and carbon-based alternatives. Here, we report a conducting polymer:cellulose composite that serves as the active material in supercapacitors which has been incorporated into all-printed energy storage devices. These devices exhibit a specific capacitance of ≈90 F g−1 and an excellent cyclability (>10 000 cycles). Further, a design concept coined ‘supercapacitors on demand’ is presented, which is based on a printing–cutting–folding procedure, that provides us with a flexible production protocol to manufacture supercapacitors with adaptable configuration and electrical characteristics.

Influence of the carbonate ion on characteristics of electrochemically synthesized layered (α+β) nickel hydroxide

Nickel hydroxide is widely used as the active material of supercapacitors. The most active are samples of Ni(OH)2 with (α+β) layered structure, synthesized in the slit diaphragm electrolyzer. Influence of carbonate anion on the structure and electrochemical properties of nickel hydroxide samples has been studied by means of sample synthesis in the slit-diaphragm electrolyzer with the use of the diaphragm and cation-exchange membrane as chamber separator. The experiment revealed that when the diaphragm is used, there is a filtration flow from the anodic chamber (alkali with carbonate) into the cathodic chamber. Thus, the samples synthesized with the diaphragm are formed in the presence of carbonates, while the samples synthesized with the cation-exchange membrane – in the absence of carbonates. Crystal structure of the samples was studied by means of X-ray diffraction analysis, electrochemical characteristics – by means of cyclic voltammetry and galvanostatic charge-discharge cycling in the accumulator regime. Comparative analysis of the samples synthesized in the presence or absence of carbonates has been conducted. By means of X-ray diffraction and cyclic voltammetry, the key role of carbonate ions in the formation of monophase layered (α+β) structure has been revealed. The absence of carbonate resulted in lower crystallinity, α-phase content, the formation of the bi-phase system, composed of the mixture of β-form and (α+β)-structure, at high current densities (12 and 15.7 A/dm2). The study of electrochemical characteristics revealed a decrease in specific capacity by 14.7–31.4 % for hydroxide samples formed in the absence of carbonate ions. The highest specific capacity was obtained for the samples synthesized in the SDE at i=10 A/dm2 with the diaphragm (in the presence of carbonates) and with the membrane (in the absence of carbonates), and are 216.8 and 185 mA·h/g respectively. To increase specific capacity, it is recommended to conduct synthesis in the SDE with the use of the diaphragm and introduce an additional quantity of sodium carbonate into the anolyte

A review of electrode materials based on core–shell nanostructures for electrochemical supercapacitors

This review article outlines the most commonly used methods for making the core/shell structures as the active materials for supercapacitors over the past decade (2007–2018), and points out the most efficient combination of the material categories and morphologies for the core/shell structure.

“The popcorn effect”: obtaining of the highly active ultrafine nickel hydroxide by microwave treatment of wet precipitate

Nickel hydroxide is widely used as an active material of supercapacitors. The most active are samples of Ni(OH) 2 with (α+β) layered structure synthesized in a slit diaphragm electrolyzer. However, the processes that occur during filtering and drying , negatively impact electrochemical activity. The influence of microwave treatment of different times (from 0.5 to 5 min) on the structure, surface morphology and porous structure, and also on the electrochemical properties of nickel hydroxide samples prepared in a slit diaphragm electrolyzer , has been studied. A hypothesis was proposed on the existence of the “popcorn effect”: short-term high-power microwave irradiation of the wet sample would result in water boiling and internal explosion of the sample. Treated and untreated samples were studied by means of X-ray diffraction analysis, scanning electron microscopy and BET nitrogen adsorption-desorption. Electrochemical characteristics were studied by means of galvanostatic charge-discharge cycling in the supercapacitor regime. The existence of the “popcorn effect” has been confirmed by increased sample thickness after microwave treatment by 1.94 times, specific surface area 2.13 times, pore volume by 2.66 times, and average pore diameter by 1.46 times, It was discovered , that increasing treatment duration to 2–5 min leads to microwave drying. XRD results revealed the occurrence of ageing (crystallization) processes of nickel hydroxide during thermal drying and their absence upon realization of the “popcorn effect”. This results in the formation of X-ray amorphous samples. Comparative analysis of electrochemical characteristics of treated and untreated Ni(OH) 2 samples was performed. An increase of specific capacity at high current densities (80 and 120 mA/cm 2 ) for treated samples was observed: by 10.9 % upon microwave drying, 24–42 % upon realization of the “popcorn effect”. The maximum capacity of 231.1 F/g has been observed for the sample, in which the “popcorn effect” was realized the most. However, microwave treatment resulted in lower capacities at low cycling current density. This is related to the thermal treatment of the particle surface, caused by rapid boiling of water. A magnetron of a higher power is required for avoiding this negative effect

A Novel CVD Growth of g‐C3N4 Ultrathin Film on NiCo2O4 Nanoneedles/Carbon Cloth as Integrated Electrodes for Supercapacitors

AbstractAlthough g‐C3N4 possesses many features such as a graphene‐like 2D π‐conjugated planar layered structure, high nitrogen content, excellent mechanical strength and flexibility, as well as high thermal and chemical stability, there are only a few studies on the exploration of g‐C3N4 as active materials for supercapacitors. This could be largely attributed to the fact that the above advantages of g‐C3N4 to hybrid with other materials are still not fully established. Herein, we successfully develop a facile low‐temperature CVD method to grow g‐C3N4 ultrathin films with several nanometers thickness on the surface of NiCo2O4 nanoneedles. Subsequently, a NiCo2O4 nanoneedles@g‐C3N4 ultrathin film core‐shell nanostructures/carbon cloth (NiCo2O4 NNs@g‐C3N4/CC) integrated electrode was obtained. Thanks to the ultrathin film, a core‐shell nanostructure, as well as intrinsic features of g‐C3N4, the as‐obtained integrated electrode displays excellent electrochemical performance, exhibiting an areal capacitance of 2.83 F cm−2 as well as high cycling stability (5.88 % loss after 10 000 cycles). Our results clearly demonstrate that the g‐C3N4 ultrathin film obtained through this facile CVD method developed has potential in hybridizing with other transition metal oxides as electrode materials for supercapacitors and, more importantly, this convenient synthesis method may also be widely used for other applications such as designing new heterojunction photocatalysts.

Tuning peptide self-assembly by an in-tether chiral center.

The self-assembly of peptides into ordered nanostructures is important for understanding both peptide molecular interactions and nanotechnological applications. However, because of the complexity and various self-assembling pathways of peptide molecules, design of self-assembling helical peptides with high controllability and tunability is challenging. We report a new self-assembling mode that uses in-tether chiral center-induced helical peptides as a platform for tunable peptide self-assembly with good controllability. It was found that self-assembling behavior was governed by in-tether substitutional groups, where chirality determined the formation of helical structures and aromaticity provided the driving force for self-assembly. Both factors were essential for peptide self-assembly to occur. Experiments and theoretical calculations indicate long-range crystal-like packing in the self-assembly, which was stabilized by a synergy of interpeptide π-π and π-sulfur interactions and hydrogen bond networks. In addition, the self-assembled peptide nanomaterials were demonstrated to be promising candidate materials for applications in biocompatible electrochemical supercapacitors.

Electrochemical Supercapacitive Performance of Spray-Deposited NiO Electrodes

Transition-metal oxides with porous structure are considered for use as promising electrodes for high-performance supercapacitors. Nanocrystalline nickel oxide (NiO) thin films have been prepared as active material for supercapacitors by spray pyrolysis. In this study, the effects of the film thickness on its structural, morphological, optical, electrical, and electrochemical properties were studied. X-ray diffraction analysis revealed cubic structure with average crystalline size of around 21 nm. Scanning electron microscopy showed porous morphology. The optical bandgap decreased from 3.04 eV to 2.97 eV with increase in the film thickness. Electrical resistivity measurements indicated semiconducting behavior. Cyclic voltammetry and galvanostatic charge/discharge study revealed good pseudocapacitive behavior. Specific capacitance of 564 F g−1 at scan rate of 5 mV s−1 and 553 F g−1 at current density of 1 A g−1 was observed. An NiO-based supercapacitor delivered specific energy of 22.8 W h kg−1 at specific power of 2.16 kW kg−1, and retained 93.01% specific capacitance at current density of 1 A g−1 after 1000 cycles. Therefore, taking advantage of the porous morphology that exists in the nanostructure, such NiO materials can be considered for use as promising electrodes for high-performance supercapacitors.

Rice Husk Derived Activated Carbon/Polyaniline Composites As Active Materials For Supercapacitors

Rice Husk Derived Activated Carbon/Polyaniline Composites As Active Materials For Supercapacitors

Three-dimensional poly(aniline- co -pyrrole)/thermally reduced graphene oxide composite as a binder-free electrode for high-performance supercapacitors

Abstract Three-dimensional poly(aniline-co-pyrrole)/thermally reduced graphene oxide (PAP/TRGO) composites with different amounts of TRGO have been fabricated via an oxidative polymerization method. The three-dimensional composite containing 20 wt% TRGO exhibits enhanced electrochemical performance as an electrode active material in supercapacitors in terms of its high specific capacitance value (287 F g−1 at 0.2 A g−1) and good rate capability (205 F g−1 at 20 A g−1). The assembled symmetric supercapacitor based on the PAP/TRGO20 composite shows excellent cyclic stability with a capacitance retention of 103% after 10,000 charge-discharge cycles. These results represent a significant progress in the design of suitable binder-free electrode materials as electrochemical energy storage devices.

Synthesis and characterization of micro-composites: For enhanced electrochemical properties

In this study, we describe an experimental investigation on synthesis and characterization of silicon carbide (SiC) particles encapsulated with MgO (magnesium oxide) and nanocrystalline MgAl2O4 spinel (magnesium aluminate), respectively through sol− gel route, a facile technique. Synthesized microcomposites were comprehensively examined by various characterization techniques like FE-SEM (Field emission scanning electron microscopy), XRD (X-Ray diffraction) and TEM (Transmission electron microscopy), respectively. Elemental mapping and X-ray energy dispersion spectroscopy (EDX) associated with high-resolution SEM provided the specific amount of shell materials. Furthermore, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) examination was conducted for the MgO encapsulated SiC and MgAl2O4 encapsulated SiC microcomposites. The synthesized encapsulated SiC with MgAl2O4 spinel is having a better catalytic ability and show higher peak currents compared to MgO decorated SiC and pristine SiC. The results obtained from EIS and CV testing demonstrate that synthesized microcomposites can be applied as an active material for supercapacitors, fuel cells, electronic devices, electrodes and unique reinforcing materials in other metal as well as polymer matrix, respectively.

3D flower-like CoS hierarchitectures recycled from spent LiCoO2 batteries and its application in electrochemical capacitor

As more and more lithium ion batteries are scrap to recycle in recent years, developing high-efficient recycling method is crucial and urgent. In this paper, LiCoO2 wastes are employed and the cobalt source is recycled as an active material for supercapacitor, while the lithium source can be recycled as Li2CO3. The recycled CoS exhibits a 3D flower-like morphology and superb electrochemical capacity can be obtained due to the unique structure. This method can provide a new thinking to battery recycling, which can be also applied to other battery wastes.

Reduced Graphene Oxide/α-Fe2O3 Fibres as Active Material for Supercapacitor Application

The composite hydrogel, composed of reduced graphene oxide and α-Fe2O3 fibres (rGO/α-Fe2O3), was successfully prepared by the hydrothermal procedure starting from GO and α-Fe2O3 nanofibres. According to the SEM and XRD results, α-Fe2O3 fibres are distributed between rGO sheets increasing the inter-sheet space. The rGO/α-Fe2O3 composite was tested as an active material in supercapacitor by means of cyclic voltammetry, galvanostatic charging/discharging and electrochemical impedance spectroscopy in 0.5 mol dm–3 Na2SO4. The obtained results confirmed a positive effect of the α-Fe2O3 addition on capacitive properties. Improved capacitive properties of the composite make this material suitable for supercapacitor application.

Photo-Reduced Graphene as Electrode Active Materials for Supercapacitor Applications

Graphene is a form of carbon that has high electrical conductivity, a planar structure and substantially high surface area, thereby having the potential for more storage of electrostatic charge for high energy supercapacitors (SC). In this paper, the recent developments on the fabrication of graphene by means of photo-reduction of graphene oxide will be overviewed. The main advantage of the photo-process is that it does not rely on the use of chemicals or high temperature. For example, KrF excimer laser irradiation process for the fabrication of N-doped graphene from graphene oxide will be illustrated and the performance of laser reduced N-doped graphene when it is used as electrode active materials in supercapacitors will also be evaluated.

Photo-Reduced Graphene As Electrode Active Materials for Supercapacitor Applications

Supercapacitors are among the most promising energy storage devices due to their high power density, short recharging time, long cycle life, as well as environmental friendliness. Supercapacitors with increased energy densities are needed for practical applications such as plug-in hybrid electric vehicles, wind turbine energy storage, regenerative breaking, cold starting of trucks and space exploration applications. Supercapacitors store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). Electrochemical double layer capacitors use the high surface area of carbon, such as activated carbon, carbon fiber and graphene, as the electrode active materials, while metal oxides and electronically conducting polymers are used as the electrode active materials for pseudo-capacitors. Graphene is a form of carbon that has substantially higher surface area than the more common electrode active material, activated carbon, and thus potentially allows for more storing of electrostatic charge. The high electrical conductivity and planar structure of graphene also gives rise to fast charging and discharging. In this presentation, recent development on the fabrication of graphene by means of photo reduction of graphene oxide will be given. The photo reduction creates a disordered corrugated graphene structure in which adjacent sheets are no longer oriented parallel to each other. As an example, the performance of excimer laser reduced graphene and N-doped graphene when it is used as electrode active materials in supercapacitors was evaluated in both aqueous and organic electrolytes at room temperature. By varying the laser irradiation processing conditions such as laser energy and irradiation time, graphene and N-doped graphene with different supercapacitive behaviors were successfully grown. The specific capacitance of laser reduced graphene reaches 120 F/g at 5mV/sec in the aqueous electrolyte. Highly conductive N-doped graphene can be prepared by adding NH3 into graphene oxide solution during laser photo-reduction process and the doped graphene has slightly reduced specific capacitance of 110 F/g at 5 mV/sec in 0.5 M K2SO4 aqueous electrolyte. This work demonstrated that excimer laser irradiation process is a very promising technique for preparation of graphene and N-doped graphene for its use as the electrode active material for supercapacitors due to its excellent flexibility and capability of controlling microstructures, electric conduction and specific capacitance. Figure 1

Enhanced electrochemical performance of nickel-cobalt-oxide@reduced graphene oxide//activated carbon asymmetric supercapacitors by the addition of a redox-active electrolyte

Supercapacitors are an emerging energy-storage system with a wide range of potential applications. In this study, highly porous nickel-cobalt-oxide@reduced graphene oxide (Ni-Co-O@RGO-s) nanosheets were synthesized as an active material for supercapacitors using a surfactant-assisted microwave irradiation technique. The RGO-modified nanocomposite showed a larger specific area, better conductivity, and lower resistivity than the unmodified nanocomposite because the RGO facilitated faster ion diffusion/transport for improved redox activity. The synergistic effect of Ni-Co-O@RGO-s resulted in a high capacitance of 1903Fg−1 (at 0.8Ag−1) in a mixed KOH/redox active K3Fe(CN)6 electrolyte. The asymmetric Ni-Co-O@RGO-s//AC supercapacitor device yielded a high energy density and power density of 39Whkg−1 and 7500Wkg−1, respectively. The porous structure and combination of redox couples from both the electrode and electrolyte provided a highly synergistic effect, which improved the performance of the supercapacitor device.

Electrosynthesis and characterization of poly aniline/garnet nanoparticles for high-performance electrochemical capacitors

In this work, supercapacitive performance of polyaniline/yttrium aluminum garnet (YAG: Y3Al5O12) nanoparticles (PANI/YAGNPs) was studied. YAG nanoparticles were synthesized by pulse electro-deposition method and after that, PANI/YAGNPs electrodeposited on the surface of glassy carbon electrodes through cyclic voltammetry. Morphological studies show that YAG nanoparticles were distributed in the structure of PANI filaments uniformly. XRD and FTIR were used to perform a structural study of materials. Different electrochemical techniques such as cyclic voltammetry (CV), galvano static charge discharge (CD), and impedance spectroscopy (EIS) were used to evaluate the applicability of using PANI/YAGNPs as an active material for supercapacitors. The specific capacitance (SC) of PANI and PANI YAG NPs electrodes calculated using CV technique are 240 and 440 F/g, respectively. Increasing the conductivity and stability of composite electrodes during continuous CD cycles compared to PANI ones are some features of using YAG NPs in the structure of polymer electrodes. Stability of composite electrodes remains about 98% through 1000 continuous cycles whereas the polymeric electrode loses about 91% of its capacitance during this time range.

Unveiling Polyindole: Freestanding As-electrospun Polyindole Nanofibers and Polyindole/Carbon Nanotubes Composites as Enhanced Electrodes for Flexible All-solid-state Supercapacitors

Polyindole(Pind) is one of the conducting polymers (CPs) which previously was less studied but of recent is gaining attention for energy storage applications. In all the few previous reports, when Pind was employed as electrode active material in supercapacitors, the capacitance was reported low with reasonable values only being obtained as a composite with other materials. The reasons underlying the poor performance of Pind and Pind nanocomposites are thought to be: 1) inactive morphology and limited surface area, 2) poor conductivity, and 3) poor electrode fabrication techniques. To address the trio, we employed the traditional, easy and scalable electrospinning technique to fabricate high surface area electroactive Pind nanofibers. Further, a little percentage (10wt.%) of carbon nanotubes (CNTs) were added to enhance the conductivity of Pind and to study the effect of our fabrication route on the nanocomposites. Significant capacitance improvements of up to 238Fg−1 and 476Fg−1 at 1.0Ag−1 for Pind and Pind/CNT freestanding electrospun electrodes, respectively were achieved. Moreover, we report the significant performance of the all-solid-state symmetric, flexible and binder-free supercapacitor fabricated by a one-step and scalable method of as-electrospun Pind/CNT nanofibers on the stainless steel fabric current collector. The supercapacitor showed a high energy density of 17.14W h kg−1 at a power density of 426Wkg−1 and capacitance retention of 95% after 2000 cycles. We strongly believe that we have set a stage for Pind to compete in a healthy race with other CPs as a next generation electrode material for supercapacitors.

Interfacial characterization and supercapacitive properties of polyaniline—Gum arabic nanocomposite/graphene oxide LbL modified electrodes

In this manuscript, we describe the synthesis and electrochemical characterization of polyaniline—gum arabic nanocomposites and graphene oxide (PANI-GA/GO) modified electrodes with a detailed study concerning their supercapacitive properties. The electrode modification was carried out by using the Layer-by-Layer technique (LbL), where the PANI-GA nanocomposite dispersion was used as polycation and the GO colloidal dispersion as polyanion. The bilayer growth was followed by both UV–vis spectroscopy and cyclic voltammetry, and an increase in the characteristic PANI absorption and in the electrochemical signal was verified, confirming the electrode build up. Galvanostatic charge-discharge curves (GCDC) were performed to evaluate the supercapacitive properties of the modified electrodes, these results showed the dependence of the specific capacitance with the number of bilayers, where values of CS around 15mFcm−2 (i=0.1mAcm−2) were found. Electrochemical impedance spectroscopy confirmed the pseudocapacitive properties of the modified electrodes, showing an increase in the low-frequency capacitance with the number of bilayers. Hereby the (PANI-GA/GO)-LbL electrodes were shown to be good candidates for active materials in supercapacitors.