Active Material For Supercapacitors Research Articles

Hydrazine reduction of LaNiO3 for active materials in supercapacitors

AbstractTo improve the electric conductivity and overall performance of active materials in pseudocapacitors, we have established a novel hydrazine reduction process to transform perovskite oxides into active materials with the desired electrical conductivity and electrochemical behavior. Taking LaNiO3 (LNO) produced from chemical solution as the starting material, different durations of hydrazine reduction (e.g. from 3, 6 to 12 hours) leads to a significant increase in specific capacitance, from ~70 F·g−1 at 1 A·g−1 (LNO) to ~280 F·g−1 at 1 A·g−1 (after 12 hours reduction). The desired electrical conductivity of LNO has been retained, as shown by the overall resistance of less than 0.3 Ω in the aqueous electrolyte. The hydrazined LNO demonstrated the desired stability as electrode, where the porous structure provides better accessibility for electrolytes, which is helpful in enhancing the overall electrochemical behaviors.

Commercialized Benzoxazine Resin-Derived Porous Carbon as high Performance Electrode Materials for Supercapacitor

A novel porous carbon C–(BA-a) has been simply synthesized from a commercialized benzoxazine resin (BA-a) using a soft-templating method. The chemical structure of BA-a has been confirmed by 1H nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FT-IR) and its polymerization behavior is monitored by in situ FT-IR and differential scanning calorimetry (DSC). In order to increase the active site of surface electrochemical reactions and promote the wettability in aqueous electrolyte, a facile chemical surface activation is used on C–(BA-a) by nitric acid. The acid-modified porous carbon, N–C–(BA-a), is applied as the active materials for supercapacitors using Na2SO4 as an eco-friendly electrolyte. After acid treatment, the N–C–(BA-a) exhibits the largest specific capacitance of 99.94 F g−1 at a current density of 0.1 A g−1 in 1 M Na2SO4 electrolyte, which is more than 16 times larger than that of the C–(BA-a). Additionally, the N–C–(BA-a) possesses excellent cycling stability over 5000 cycles, suggesting its potential application for supercapacitors.

Electrodeposition of polyaniline in long TiO2 nanotube arrays for high-areal capacitance supercapacitor electrodes

Anodic TiO2 nanotube arrays (TNTAs) were found to be a suitable scaffold for the loading of other active materials for supercapacitors. The prepared coaxial nanostructured composite-based TNTAs have been reported to show a remarkable specific capacitance. However, owing to the semiconductive nature of TiO2 and the diffusion limits of electrolytes in nanotubes, the electrodeposition of active materials was often found to preferentially occur at the upper areas of TNTAs, resulting in insufficient pore filling especially for long nanotubes. Here, robust and long (over 100 μm) TNTAs are served as a support template for electrodeposition of polyaniline (PANI). After an electrochemical reduction process of TNTAs, uniform and complete pore filling with PANI using electrodeposition from bottom to top is realized by potentiodynamic cycling successfully. The obtained PANI/TNTAs composites show areal capacitances as high as 512.4 mF cm−2 due to the higher loadings of PANI. They also have relatively good rate capability and cycling stability. This work makes PANI/TNTAs composite electrodes really scalable.

Softwood Lignin as a Sustainable Feedstock for Porous Carbons as Active Material for Supercapacitors Using an Ionic Liquid Electrolyte

We report on the facile synthesis of porous carbons based on a biopolymer lignin employing a two-step process which includes the activation by KOH in various amounts under an inert gas atmosphere. The resulting carbons are characterized with regard to their structural properties and their electrochemical performance as an active material in double-layer capacitors using for the first time an ionic liquid (EMIBF4) as the electrolyte for this type of carbon material to enhance storage ability. A capacitance of more than 200 F g–1 at 10 A g–1 is achieved for a carbon with a specific surface area of more than 1800 m2 g–1. One of the most crucial factors determining the electrochemical response of the active materials was found to be the strong surface functionalization by oxygen-containing groups. Furthermore, the sulfur content of the carbon precursor lignin does not result in a significant amount of sulfur-containing surface functionalities which might interact with the electrolyte.

Electrochemical Preparation of Polypyrrole/Graphene Films on Titanium Mesh as Active Materials for Supercapacitors

Films of polypyrrole/graphene on titanium mesh were prepared by electrochemical reduction of the fresh dried foam films of graphene oxide followed by an electrochemical polymerization of pyrrole. The as-obtained composite had highly surface area, conductivity, and could be used as the electrode for supercapacitors, especially directly used as the active materials in free of binders while the Ti mesh worked as the collector. Plenty of polypyrrole nanoparticles formed on the surface of reduced graphene film, and some fiber-like aggregates could be formed during the polymerization, which worked as the material for pseudo-capacitance. The specific capacitance of the supercapacitor reached 400 F/g and showed high stability with retaining capacitance of 82% after 5000 cycles, indicating that the nanocomposite is a suitable active material for supercapacitors.

Synthesis of peanut-like hierarchical manganese carbonate microcrystals via magnetically driven self-assembly for high performance asymmetric supercapacitors

Peanut-like hierarchical MnCO3 microcrystals assembled with floss-like nanowires are synthesized via a hydrothermal process and used as an active material for supercapacitors.

Synthesis and Integration of Ultrathin Polyaniline Films into Carbide Derived Carbon Supercapacitors

Utilizing conducting polymers as the active materials for supercapacitors is a novel and promising approach to improve performance [1-4]. Conducting polymers have been shown to have high specific capacity, high energy density, and promising stability. Furthermore, they are less costly than oxide-based materials and have the ability to be p and n-doped. Moreover, conducting polymers enhance charge capacity through Faradaic redox reactions. As reported by Simon and Gogotsi [5], the integration of ultrathin pseudocapacitive materials within porous carbon nanostructures can result in significant improvement in energy and power densities, allowing for having both battery-like (high capacity) and capacitor-like (high rate) behavior in a single electrode. Conducting polymers are typically deposited via solvent-based techniques such as chemical bath deposition, electrodeposition, and casting from suspension. Nevertheless, challenges exist with making uniform conformal coatings, especially with poor solubility of many conducting polymers and poor accessibility of the highly tortuous pore space within nanostructured electrodes. Oxidative chemical vapor deposition (oCVD) allows one to conveniently bypass these challenges as it is a solvent-free method where the reagents for oxidative polymerization, the monomer and oxidizer, are heated to vapor form that can easily penetrate into mesoscale pores and polymerize (Figure 1). By understanding the oCVD PANI synthesis parameters (reagent flow rates, reactor pressure, substrate temperature, saturation pressure), the reaction and diffusion rates can be carefully controlled to optimally coat the CDC electrode. By flowing vapors of aniline and antimony pentachloride (a strong oxidizer), a solid thin PANI film can be polymerized on a substrate. FTIR, UV-vis, and XPS confirm that oCVD produces the electrochemically active emeraldine state of PANI. The pore distribution of the CDC electrode, as determined by N2 sorption, remains mostly unchanged before and after coating because the fine oCVD control over film thickness allows the pores to be coated without filling them, thereby maintaining the electrochemical double layer of the intrinsic carbon electrode while imparting additional energy density through Faradaic redox reactions from PANI. In this work, we demonstrate that charge storage capacity can be improved significantly through the integration of ultrathin (<30 nm) polyaniline (PANI) films into bimodal mesoporous Mo2C-derived carbide derived carbon (CDC, 800 °C synthesis temperature) electrodes using a single-step oCVD process. The ultrathin coating preserves to a large extent the native electrode surface area and pore distribution while simultaneously improving capacitance. The oCVD process allows PANI to be integrated into pores as small as 1.7 nm, and the oCVD PANI integrated supercapacitors have a specific capacitance more than 100% higher than that of bare CDC ones (136 F/g for 11 wt% of PANI in the CDC electrode vs. 60 F/g for bare CDC at 10 mV/s). This yields a PANI-only capacitance of ~690 F/g, which is close to the theoretical value of 750 F/g [6]. Even after high scan rates of over 100 mV/s, the added pseudocapacitance from PANI remains evident (Figure 1). The composite device exhibits excellent cyclability, lowering to only 90% of the initially stabilized value (~100 F/g) after 10,000 cycles. To our knowledge, this work is the first reported synthesis of PANI via oCVD and demonstrates oCVD’s advantages compared to other approaches in the integration of ultrathin PANI films into carbon supercapacitors. Figure 1. Left: oCVD process where the oxidant (SbCl5, orange) and monomer (aniline, green) vapors enter the reaction chamber and surface polymerize onto the electrode. Middle: A comparison of the cyclic voltammograms for both bare (red) and polyaniline (PANI) (green) electrodes at 20 mV/s. Inset shows SEMS of bare and PANI-coated CDC electrodes. Right: Rate performance of both devices based on cyclic voltammetry. [1] A. Laforgue, P. Simon, C. Sarrazin, J.-F. Fauvarque, Journal of Power Sources, 80 (1999) 142-148. [2] D.Y. Liu, J.R. Reynolds, ACS Applied Materials & Interfaces, 2 (2010) 3586-3593. [3] A. Rudge, I. Raistrick, S. Gottesfeld, J.P. Ferraris, Electrochimica Acta, 39 (1994) 273-287. [4] S. Nejati, T.E. Minford, Y.Y. Smolin, K.K.S. Lau, ACS Nano, 8 (2014) 5413-5422. [5] P. Simon, Y. Gogotsi, Nature Materials, 7 (2008) 845-854. [6] G.A. Snook, P. Kao, A.S. Best, Journal of Power Sources, 196 (2011) 1-12. Figure 1

Enhancing effect of boron trifluoride diethyl etherate electrolytes on capacitance performance of electropolymerized poly[poly(N-vinyl-carbazole)] films

In this paper, poly[poly(N-vinyl-carbazole)] (PPVK) films electrodeposited in tetrahydrofuran (THF) containing 12 % boron trifluoride diethyl etherate (BFEE) were studied as electrode active material for supercapacitors. The morphology and thermal property were characterized by SEM, atomic force microscopy (AFM), and thermogravimetry (TG), respectively. The electrochemical capacitive behaviors of the PPVK films were also investigated by cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy. The electrochemical results showed that the specific capacitance of PPVK films in CH3CN solution was about 126 mF cm−2 at 1.5 mA cm−2 and the capacitance retention was only 14.4 % after 1000 cycles. It was exciting to improve the specific capacitance up to 169.3 mF cm−2 at 1.5 mA cm−2 and to make the cyclic stability increase to 81.8 % capacitance retention after 5000 cycles when the equivalent BFEE was added into the CH3CN solution containing 0.05 M Bu4NBF4 electrolyte. These results clearly demonstrated that BFEE was an efficient promoter for the enhancement of the capacitance performance of PPVK films. Therefore, with the help of BFEE electrolyte, the PPVK films have potential application as capacitive materials in high-performance energy storage devices.

Synthesis of NiMnO3/C nano-composite electrode materials for electrochemical capacitors

Demand for high-performance energy storage materials has motivated research activities to develop nano-engineered composites that benefit from both high-rate and high-capacitance materials. Herein, NiMnO3 (NMO) nanoparticles have been synthesized through a facile co-precipitation method. As-prepared NMO samples are then employed for the synthesis of nano-composites with graphite (Gr) and reduced graphene oxide (RGO). Various samples, including pure NMO, NMO-graphite blend, as well as NMO/Gr and NMO/RGO nano-composites have been electrochemically investigated as active materials in supercapacitors. The NMO/RGO sample exhibited a high specific capacitance of 285 F g−1 at a current density of 1 A g−1, much higher than the other samples (237 F g−1 for NMO/Gr, 170 F g−1 for NMO-Gr and 70 F g−1 for NMO). Moreover, the NMO/RGO nano-composite has shown excellent cycle stability with a 93.5% capacitance retention over 1000 cycles at 2 A g−1 and still delivered around 87% of its initial capacitance after cycling for 4000 cycles. An NMO/RGO composite was assessed in practical applications by assembling NMO/RGO//NMO/RGO symmetric devices, exhibiting high specific energy (27.3 Wh kg−1), high specific power (7.5 kW kg−1), and good cycle stability over a broad working voltage of 1.5 V. All the obtained results demonstrate the promise of NMO/RGO nano-composite as a high-performance electrode material for supercapacitors.

Synthesis of hierarchically porous MnO2/rice husks derived carbon composite as high-performance electrode material for supercapacitors

Hierarchically porous MnO2/rice husks derived carbon (MnO2/RHC) composite with excellent electrochemical properties has been prepared as active material for supercapacitors. In this study, a two-step process was utilized for constructing this composite, involving carbonization–activation of rice husks to obtain RHC and in situ chemical precipitation to incorporate MnO2. Ultimately, MnO2 was uniformly distributed on the surface of RHC and hierarchically porous structure was well retained in the resultant MnO2/RHC composite. Based on cyclic voltammetry and galvanostatic charge–discharge measurements in 0.5M Na2SO4 solution, MnO2/RHC composite exhibits much higher specific capacitance than that of RHC. The specific capacitance of MnO2/RHC composite reaches 197.6Fg−1 at the scan rate of 5mVs−1 and 210.3Fg−1 at the current density of 0.5Ag−1. MnO2/RHC composite also displays favorable cycling stability with 80.2% capacitance retention after 5000 galvanostatic charge–discharge cycles. Therefore, taking advantage of the interconnected hierarchical pores that exist in its microstructure, MnO2/RHC composite is supposed to be a promising electrode material for high-performance supercapacitors.

Hierarchically nanostructured hollow carbon nanospheres for ultra-fast and long-life energy storage

We report on the successful application of porous hollow carbon nanospheres consisting of graphitic shells with a hierarchical porosity that were obtained by carbonizing an iron-containing commercially available metal-organic framework, as active material for supercapacitors. The influence of basic key parameters, such as the degree of graphitization and the accessible surface area of the carbons obtained at different temperatures, on the electrochemical performance is discussed in-depth. A high specific capacitance of 91 F g−1 in an aqueous electrolyte and 156 F g−1 using an ionic liquid is achieved. Furthermore a very steady specific capacitance over the course of 10,000 charge-discharge cycles is demonstrated. In addition, electrochemical impedance spectroscopy studies revealed that these carbons can feature a stable performance over several orders of magnitude of frequency, which render them interesting candidates for future electrochemical energy storage systems.

An asymmetric supercapacitor with ultrahigh energy density based on nickle cobalt sulfide nanocluster anchoring multi-wall carbon nanotubes hybrid

The development of novel electrode materials with high energy density and long cycling life is critical to realize electrochemical capacitive energy storage for practical applications. In this paper, the hybrids of nickle cobalt sulfide/multi-wall carbon nanotubes (NiCo2S4/MWCNTs) with different contents of MWCNTs are prepared using a facile one-pot solvothermal reaction. As novel active materials for supercapacitors, the electrochemistry tests show that the hybrid of NiCo2S4/MWCNTs-5 is able to deliver a high specific capacitance of 2080 F g−1 at the current density of 1 A g−1, even superior rate capability of 61% capacitance retention after a 20-fold increase in current densities, when the content of MWCNTs is up to 5%. More importantly, an asymmetric supercapacitor assembled by NiCo2S4/MWCNTs-5 as positive electrode and reduced graphene oxide (rGO) as negative electrode delivers a high energy density of 51.8 Wh Kg−1 at a power density of 865 W kg−1, and 85.7% of its initial capacitance is retained at the current density of 4 A g−1 after 5000 charge-discharge cycles, exhibiting potential prospect for practical applications.

Graphene and its nanocomposites used as an active materials for supercapacitors

This review article investigates the hot topics by presenting the latest advances on graphene-based nanostructures for supercapacitors. In literature, many scientists have studied the nanomaterials and combination of conducting polymers in supercapacitor (SC) devices. The main aim of this review article is to present the higher capacitance, and higher power and energy density performances of the SC devices, which includes the active materials of carbon-based materials, metal oxides, conducting polymers, nanocomposites, etc. Many conventional techniques have already been used such as photolithography, inkjet printing, etc. Each of these methods has specific advantages and some drawbacks, with some working better in different environments. Among various nanoscaled materials, nanocrystal oxides of transition metals play an important role in advanced materials development. In addition to design of active material, symmetric and asymmetric supercapacitor device fabrication is also directly effect to obtain a higher capacitance, energy and power density performances. Therefore, this review article focuses on supercapacitor technology in new developments, such as design of active materials, device fabrication, etc.

Design and Fabrication of Ni3P2O8-Co3P2O8·8H2O as Advanced Positive Electrodes for Asymmetric Supercapacitors

Nano-sized Ni3P2O8-Co3P2O8·8H2O is synthesized via a facile chemical precipitation method as the active material of supercapacitors. The experiment result expresses the Ni3P2O8-Co3P2O8·8H2O of the Ni/Co molar ratio of 8:2 exhibits enhanced capacitive behaviors relatively than others, it delivers a highest mass specific capacitance of 1974Fg−1 at 0.5Ag−1, which is higher than both Ni3P2O8 and Co3P2O8·8H2O. The sforzato in specific capacitance is on account of the pore structure, uniform particle morphology, and hyperbaric of Ni. An asymmetric supercapacitor is assembled using the Ni3P2O8-Co3P2O8·8H2O and activated carbon (AC) as positive and negative electrode, respectively. It not only sends a large specific capacitance (94Fg−1) but also good cycling stability (up to 5000 cycles). The impressive results presented here may be potential applications for high energy density storage systems.

Molten-salt treatment of waste biomass for preparation of carbon with enhanced capacitive properties and electrocatalytic activity towards oxygen reduction.

Carbon powders are building blocks for electrochemical energy storage/conversion devices. Green, cost-affordable and facile preparation of carbon with applicable electrochemical properties is therefore essential for effective utilization of fluctuating renewable energy. Herein, the preparation of carbon nanoflakes via impregnation of waste biomass i.e. boiled coffee beans in molten Na2CO3-K2CO3 (with equal mass) at 800 °C and molten CaCl2 at 850 °C is reported. The microstructure and surface chemistry of the obtained carbons are specified. The correlations between synthetic conditions and microstructure/surface chemistry of the obtained carbons are rationalized. The derived carbon nanosheets are tested and compared as active materials for supercapacitors in a configuration of symmetric full cells in 1 M MeEt3NBF4 in acetonitrile and electrocatalysts towards the oxygen reduction reaction (ORR) in O2-saturated 0.1 M aqueous KOH. Despite the lower surface area, the carbon nanosheets derived in molten Na2CO3-K2CO3 exhibit enhanced capacitive properties and electrocatalytic ORR activity. The present study highlights the importance of thermal media on the microstructure, surface chemistry and electrochemistry of carbon from biomass.

Design of a layered nanoreactor to produce nitrogen doped carbon nanosheets as highly efficient material for supercapacitors

So far, nitrogen doped carbon materials (NCMs) have been prepared by various methods for use as the active materials in supercapacitors. However, the main reason for delay in starting the practical use and commercializing the NCMs in supercapacitors is the use of very especial organics as well as many steps of the synthesis. Here we demonstrate that the NCMs can be prepared by a simple route on a very large scale using any organic anions. Nitrogen doped carbon nanosheets were prepared by design of a layered nanoreactor including gallate and nitrate anions. Under heat-treatment, the reaction between gallate and nitrate anions resulted in the production of NCM nanosheets which could be used as electrode material in supercapacitor. The produced carbon material shows highly porous structures with suitable micro/mesopores, appropriate nitrogen content and ultrahigh specific capacitance for this type of active material in supercapacitors. Electrochemical analyses declare a perfect rectangular CV, very low Ohmic resistance for charge–discharge curves at current densities up to 4 A/g and a high specific capacitance (255.5F/g at the current density of 0.5A/g) for the produced nanosheets.

Micro–mesoporous carbons from rice husk as active materials for supercapacitors

Activated carbons were prepared from rice husk carbonized in the fluidized catalysts bed reactor. Using the different activating agents, samples with BET surface area in the range from 540 to 3060 m2/g were achieved. Using sodium or potassium carbonates results in the BET surface area up to 1400 m2/g. Hydroxides of sodium or potassium yield the samples with the higher BET surface area (up to 3060 m2/g). Textural peculiarities of the carbons were studied by the adsorption of nitrogen at 77 K and of carbon dioxide at 273 K. As active materials for supercapacitors, the porous carbon samples were examined by cyclic voltammetry and chronopotentiometry in galvanostatic mode in 1 M H2SO4 as the electrolyte using home-made three-electrode electrochemical glass cell. Gravimetric capacitance of the carbons is linearly proportional to the BET surface area and reaches 230 and 196 F/g at discharge current density of 0.2 and 1 A/g, respectively, for the samples with the highest surface area.

MnO2 nanoparticles decorated on electrophoretically deposited graphene nanosheets for high performance supercapacitor

Composite of manganese dioxide and electrochemically reduced graphene oxide (MnO2/ERGO) was prepared and investigated as active material in supercapacitor. In order to synthesize the nanocomposite, a thin film of graphene oxide (GO) was formed by electrophoretic deposition (EPD) technique from an aqueous dispersion of GO on stainless steel (SS). GO/SS was electrochemically reduced to form ERGO. Two-step potential method was used to deposit MnO2 on ERGO/SS. MnO2 nanoparticles with dimensions in the range of 40–70 nm were formed as a uniform coating on ERGO/SS. Specific capacitance of MnO2/ERGO/SS is 392 F g−1 at current density of 1 A g−1 in 0.5 M Na2SO4, which was higher than 159 F g−1 for ERGO/SS. Also, MnO2/ERGO/SS shows higher power and energy densities than ERGO/SS. Due to unique structure of prepared MnO2/ERGO nanocomposite, the capacitive behavior of ERGO is improved.

Synthesis and electrochemical performance of MnO2/BC composite as active materials for supercapacitors

A series of bamboo charcoal (BC)-doped MnO2 particles were synthesized via a simple and rapid hydrothermal method and the subsequent milling process. The effects of BC doping on the structure and morphology of the products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and nitrogen adsorption/desorption measurements. The results indicate that the as-prepared MnO2 is α-MnO2 microspheres, and FESEM images show that the BC particles are homogeneously distributed and embedded in the MnO2 matrix. The 3wt.% BC-doped MnO2 particles show BET surface area of 180 m2g−1. Electrochemical test results indicatethat the MnO2-3wt.% BC composite exhibits the best electrochemical performance with initial specific capacitance of 306.9, 304.9, 300.9, 299.4 and 297.4 F g−1 at 100, 150, 200, 250 and 300mAg−1, respectively. After 500 cycles, the capacitance of the capacitor is still kept about 100% at 300mAg−1, suggesting that the MnO2-3wt.% BC composite materials can be used as ideal electrode materials in supercapacitors.

One-pot synthesis of hierarchically nanostructured Ni3S2 dendrites as active materials for supercapacitors

A facile one-pot hydrothermal route was presented for the synthesis of novel Ni3S2 hierarchical dendrites with a three-dimensional (3D) framework. Through adjusting the reaction temperature and reaction time, various morphologies of Ni3S2 nanostructures were obtained. The as-prepared Ni3S2 samples have been characterized with X-ray powder diffraction, Raman spectrum, scanning electron microscopy, and transmission electron microscopy. A possible growth mechanism was proposed to illustrate the formation procedure of Ni3S2 3D hierarchical dendrites. Moreover, the electrochemical performances of all the prepared samples used as supercapacitor electrodes were investigated by cyclic voltammerty and the galvanostatic charge/discharge tests. Interestingly, the Ni3S2 hierarchical dendrites electrode exhibits excellent electrochemical properties, which can be attributed to enough electroactive sites for redox action provided by special hierarchical dendrites with individual 3D framework.