Cathode Material For Supercapacitors Research Articles

Hollow Hierarchical Carbon Spheres Decorated with Ultrathin Molybdenum Disulfide Nanosheets as High‐Capacity Electrode Materials for Asymmetric Supercapacitors

AbstractA hierarchically structured nanocomposite consisting of ultrathin MoS2 nanosheets densely dispersed on the surface of hollow carbon spheres (MoS2@HCS) is prepared through a glucose‐assisted, one‐pot synthesis. When evaluated as the cathode material for supercapacitors, MoS2@HCS exhibits pseudocapacitive behavior in a KOH electrolyte. More importantly, the capacitive performance of MoS2@HCS can be further boosted by activating the composite electrode in a KOH solution. The activation process partially removes the carbonaceous materials covering the MoS2 surface, which leads to more exposure of active electrode materials to the electrolyte. Activated MoS2@HCS exhibits a high specific capacitance value of 458 F g−1 at 1 A g−1, which is approximately 2.5 times higher than that of the MoS2 electrode. Furthermore, MoS2@HCS exhibits remarkable cycling stability, with a capacitance retention of about 86% over 1000 cycles at 8 A g−1. To further demonstrate the practical applications of composite electrode, an asymmetric supercapacitor device (ASC) is fabricated by using activated MoS2@HCS and reduced graphene oxide as the positive and the negative electrodes, respectively. The fabricated device delivers a maximum energy density of 13.7 Wh kg−1 at a power density of 616 W kg−1. Even at a high power density of 4.9 kW kg−1, the ASC device can still retain 80% of the maximum energy density.

Fabrication of chromite spinel nanoparticles and their application as electrode materials

ABSTRACTAn approach of combining simple precipitation method and thermal annealing was developed to synthesize Co chromite spinel nanoparticles that could be applied as the cathode material for supercapacitors. The nanoparticle modified electrode displayed a high specific capacitance of 418 F/g at the scan rate of 5 mv/s in a three-electrode system.

Preparation of a tetrahydroxyphenazine-modified carbon as cathode material for supercapacitor in aqueous acid electrolyte

A procedure for the grafting of oxocarbon compounds is proposed by condensation reaction with a benzenediamine to obtain an attached-phenazine moieties. A technical proof of concept is given by the covalent capture of rhodizonic acid on the Norit activated carbon and potentiality for supercapacitors is evidenced. The composite material obtained was tested as positive electrode for aqueous supercapacitors in 1M H2SO4. The redox activity covering a wide range of potential gives an unprecedented increase in specific charge of 350% and a specific energy at the discharge 3.4 times higher than the unmodified carbon.

Facile synthesis and characterization of LiV3O8 with sheet-like morphology for high-performance supercapacitors

LiV3O8 nanosheets were successfully synthesized by a facile hydrothermal approach and subsequent calcination for the first time. The samples were characterized by XRD, FT-IR, SEM and TEM. The results showed that the phase pure LiV3O8 nanosheets with layered structures were formed. Furthermore, the electrochemical properties of LiV3O8 nanosheets were investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD). The results showed that LiV3O8 nanosheets performed a high initial specific capacitance of 288Fg−1, and the specific capacitance after 10, 40, 100 cycles was 218, 131, 98Fg−1, respectively. The good electrochemical properties made them a promising candidate as a cathode material for supercapacitors.

Highly Porous Carbon Materials Filled with Nickel Hydroxide Nanoparticles; Synthesis, Study, Application in Electrochemistry

<p>Nickel hydroxide was deposited on the surface of the porous carbon to obtain a cathode material for supercapacitors. This work is the first part of the study of Ni(OH)<sub>2</sub>/С composite, which considers the conditions of its synthesis using two types of porous carbon matrices with a highly developed specific surface area (1000–3000 m<sup>2</sup>/g) and two types of precursors (NiCl<sub>2</sub>*6H<sub>2</sub>O and Ni(N<sub>3</sub>)<sub>2</sub>). The morphology of the systems, in particular the shape and size characteristics of the hydroxide filler particles, was examined using the scanning electron microscopy, X-ray diffraction, and nitrogen adsorption-desorption at 77 K. The measurements of capacity of the Ni(OH)<sub>2</sub>/С-electrodes were made in 6 M KOH using an asymmetric two-electrode cell (a porous carbon material with known electrode characteristics was employed as the counter electrode). The capacity was shown to decrease by 22–56% with increasing the scanning rate from 10 to 80 mV/s. A maximum capacity of the composite was obtained at a scanning rate of 10 mV/s was 346 F/g.</p>

Facile Hydrothermal Synthesis of Feather-like Nickel Phosphite As Cathode Materials for Supercapacitors

Recently, supercapacitors have attracted plenty of attentions, due to its high power density, long cycling lifespan and excellent stability. According to the charge storage mechanism, supercapacitors can be divided into double layer capacitors and pseudocapacitors. Moreover, the pseudocapacitors depend on faradic reaction and can result in much higher specific capacitance than double layer capacitors. For instance, nickel-based compounds exhibit outstanding performance reported in many literatures. In this work, we successfully synthesize the feather-like nickel phosphite via a facile hydrothermal route at 200 ℃ for 24 h, employing Ni(NO3)2 as nickel source, sodium pyrophosphate as phosphorus source and the mixture of deionized water and glycol as solvent. The diffraction peaks of the product are well matched with the standard diffraction patterns of the orthorhombic Ni(HPO3) (H2O) (JCPDS NO. 01-082-0075) as shown in Figure 1a. The SEM image in Figure 1b reveals the morphology of the sample is feather-like structure. Figure 2a exhibits cyclic voltammetry curves of the nickel phosphite in 6 M KOH electrolyte at different scan rate from 1 to 50 mV s-1, which indicates the electrode is highly reversible with excellent electrochemical capability and redox processes. The galvanostatic charge-discharge curves measured at different current densities are shown in Figure 2b. The corresponding specific capacitance values of the nickel phosphite are calculated from the discharge curves as shown in Figure 2c. Figure 2d shows the Nyquist plots of the nickel phosphite. Therefore, the nickel phosphite were good candidates for high performance energy storage. Figure 1

High energy density asymmetric supercapacitor based on NiOOH/Ni3S2/3D graphene and Fe3O4/graphene composite electrodes.

The application of the composite of Ni3S2 nanoparticles and 3D graphene as a novel cathode material for supercapacitors is systematically investigated in this study. It is found that the electrode capacitance increases by up to 111% after the composite electrode is activated by the consecutive cyclic voltammetry scanning in 1 M KOH. Due to the synergistic effect, the capacitance and the diffusion coefficient of electrolyte ions of the activated composite electrode are ca. 3.7 and 6.5 times higher than those of the Ni3S2 electrode, respectively. Furthermore, the activated composite electrode exhibits an ultrahigh specific capacitance of 3296 F/g and great cycling stability at a current density of 16 A/g. To obtain the reasonable matching of cathode/anode electrodes, the composite of Fe3O4 nanoparticles and chemically reduced graphene oxide (Fe3O4/rGO) is synthesized as the anode material. The Fe3O4/rGO electrode exhibits the specific capacitance of 661 F/g at 1 A/g and excellent rate capability. More importantly, an asymmetric supercapacitor fabricated by two different composite electrodes can be operated reversibly between 0 and 1.6 V and obtain a high specific capacitance of 233 F/g at 5 mV/s, which delivers a maximum energy density of 82.5 Wh/kg at a power density of 930 W/kg.

One-pot hydrothermal synthesis of Mn3O4 nanorods grown on Ni foam for high performance supercapacitor applications

Mn3O4/Ni foam composites were synthesized by a one-step hydrothermal method in an aqueous solution containing only Mn(NO3)2 and C6H12N4. It was found that Mn3O4 nanorods with lengths of 2 to 3 μm and diameters of 100 nm distributed on Ni foam homogeneously. Detailed reaction time-dependent morphological and component evolution was studied to understand the growth process of Mn3O4 nanorods. As cathode material for supercapacitors, Mn3O4 nanorods/composite exhibited superior supercapacitor performances with high specific capacitance (263 F · g-1 at 1A · g-1), which was more than 10 times higher than that of the Mn3O4/Ni plate. The enhanced supercapacitor performance was due to the porous architecture of the Ni foam which provides fast ion and electron transfer, large reaction surface area, and good conductivity.

Simple Synthesis of Amorphous NiWO4 Nanostructure and Its Application as a Novel Cathode Material for Asymmetric Supercapacitors

This study reports a simple synthesis of amorphous nickel tungstate (NiWO4) nanostructure and its application as a novel cathode material for supercapacitors. The effect of reaction temperature on the electrochemical properties of the NiWO4 electrode was studied, and results demonstrate that the material synthesized at 70 °C (NiW-70) has shown the highest specific capacitance of 586.2 F g(-1) at 0.5 A g(-1) in a three-electrode system. To achieve a high energy density, a NiW-70//activated carbon asymmetric supercapacitor is successfully assembled by use of NiW-70 and activated carbon as the cathode and anode, respectively, and then, its electrochemical performance is characterized by cyclic voltammetry and galvanostatic charge-discharge measurements. The results show that the assembled asymmetric supercapacitor can be cycled reversibly between 0 and 1.6 V with a high specific capacitance of 71.1 F g(-1) at 0.25 A g(-1), which can deliver a maximum energy density of 25.3 Wh kg(-1) at a power density of 200 W kg(-1). Furthermore, this asymmetric supercapacitor also presented an excellent, long cycle life along with 91.4% specific capacitance being retained after 5000 consecutive times of cycling.

Manganese hexacyanoferrate/MnO2 composite nanostructures as a cathode material for supercapacitors

A composite of manganese hexacyanoferrate (MnHCF) coated by an amorphous manganese dioxide layer was synthesized by a facile co-precipitation method and a further step called “deep electro-oxidation”. The structure and components of the resulting MnHCF/MnO2 composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Electrochemical testing showed a capacitance of 225.6 F g−1 at a sweep rate of 5 mV s−1 within a voltage range of 1.3 V and a high energy density of 74.5 W h kg−1 at a current density of 0.5 A g−1 during galvanostatic charge/discharge cycles, which is superior to most cathode materials, including some reported graphene/MnO2 nanocomposites. It is confirmed that the two components, manganese hexacyanoferrate and manganese dioxide, lead to an integrated electrochemical behavior and a capacitor with enhanced performance. The electrochemical testing and corresponding XPS analysis also demonstrated that the manganese coordinated by cyanide groups via nitrogen atoms in MnHCF did not get involved in the charge storage process during potential cycles.

Study on different power and cycling performance of crystalline KxMnO2·nH2O as cathode material for supercapacitors in Li2SO4, Na2SO4, and K2SO4 aqueous electrolytes

The charge/discharge, electrochemical impedance, cyclic voltammogram, and cycling behaviors of crystalline KxMnO2·nH2O as cathode material for supercapacitors in Li2SO4, Na2SO4, and K2SO4 electrolytes were compared. The different power and cycling performance of KxMnO2·nH2O during charge/discharge in the three electrolytes were elucidated by analyzing its composition and structure evolution. Compared with the Li2SO4 and Na2SO4 electrolytes, the highest ionic conductivity of K2SO4 electrolyte, the fastest charge-transfer process and slightest structural evolution of KxMnO2·nH2O during charge/discharge in the K2SO4 electrolyte lead to a superior power and cycling behavior for supercapacitor application.

Sparse MnO2 nanowires clusters for high-performance supercapacitors

MnO2 nanowires clusters are electrodeposited onto Ni foam by a cyclic voltammetric technique. MnO2 nanowires, about 20nm in diameter and up to 200nm in length, present a sparse grass clusters structure. As cathode material for supercapacitors, MnO2 nanowires clusters exhibit superior pseudocapacitance performances with high specific capacitances (1080Fg−1 at 4Ag−1 and 415Fg−1 at 30Ag−1) as well as excellent large-current cycling stability, making it suitable for high-performance supercapacitor application. The improved pseudocapacitance performances are attributed to small size, large surface area and high dispersion degree of MnO2 NWs, as well as 3-Dimension structure of Ni foam, which provide faster ion and electron transfer, larger reaction surface area, higher electrochemical activity, leading to faster reaction kinetics and higher material utilization ratio.

Hierarchically porous Co3O4 film prepared by hydrothermal synthesis method based on colloidal crystal template for supercapacitor application

Hierarchically porous Co3O4 film is prepared via a hydrothermal synthesis method based on a self-assembled monolayer polystyrene (PS) spheres template. The as-prepared Co3O4 film shows a two-layer structure: substructure is composed of Co3O4 monolayer hollow-sphere array and the superstructure consists of porous net-like Co3O4 nanoflakes possessing continuous mesopores ranging from 2 to 5nm. The pseudocapacitive behavior of the hierarchically porous Co3O4 film is investigated by cyclic voltammograms (CV) and galvanostatic charge–discharge tests in 2M KOH. As cathode material for supercapacitors, the hierarchically porous Co3O4 film exhibits noticeable pseudocapacitive properties with a capacitance of 454Fg−1 at 2Ag−1 as well as quite good cycling stability and high capacitance retention. Compared to the film prepared without template, the hierarchically porous film exhibits weaker polarization, higher capacitances and better cycling performance. The enhancement of pseudocapacitive properties are due to the hierarchically porous architecture, which provides fast ion/electron transfer and alleviates the structure degradation caused by volume expansion during the cycling process.

Porous Co(OH)2/Ni composite nanoflake array for high performance supercapacitors

Porous Co(OH)2/Ni composite nanoflake array is prepared by combing hydrothermal synthesis and electrodeposition methods. The as-prepared Co(OH)2/Ni composite nanoflake array exhibits a highly porous array structure composed of free-standing nanoflakes with thicknesses of 35–40nm. The pseudocapacitive behavior of the Co(OH)2/Ni composite nanoflake array is investigated by cyclic voltammograms (CV) and galvanostatic charge–discharge tests in 2M KOH. As cathode material for supercapacitor, the porous Co(OH)2/Ni composite nanoflake array exhibits weaker polarization, higher electrochemical activity and better cycling performance as compared to the unmodified Co(OH)2 nanoflake array. The Co(OH)2/Ni composite nanoflake array shows specific capacitances of 1310Fg−1 at 1Ag−1 and 1148Fg−1 at 40Ag−1, much higher than those of the unmodified Co(OH)2 nanoflake array (1017Fg−1 at 1Ag−1 and 775Fg−1 at 40Ag−1). The enhancement of supercapacitor properties is due to the introduction Ni in the composite array, which improves the electric conductivity of the film electrode with fast reaction kinetics.

Hierarchically porous Co 3O 4 film with mesoporous walls prepared via liquid crystalline template for supercapacitor application

Hierarchically porous Co 3O 4 film is prepared by a cathodic electrodeposition via liquid crystalline template. The as-prepared Co 3O 4 film has a net-like structure of interconnected nanoflakes with a thickness of 15–20 nm. Interestingly, the Co 3O 4 nanoflakes possess mesoporous walls ranging from 2 to 3 nm. As cathode material for supercapacitors, the hierarchically porous Co 3O 4 film exhibits superior supercapacitor performances with high specific capacitances (443 F g − 1 at 2 A g − 1 and 334 F g − 1 at 40 A g − 1 ) as well as excellent cycle life, making it suitable for high-performance supercapacitor application. The improved supercapacitor performances are due to its unique hierarchically porous morphological characteristics, which provide fast ion and electron transfer, large reaction surface area, resulting in fast reaction kinetics.

Study of activated nitrogen-enriched carbon and nitrogen-enriched carbon/carbon aerogel composite as cathode materials for supercapacitors

An activated nitrogen-enriched carbon (ANC) material and a novel activated nitrogen-enriched carbon/carbon aerogel (ANC/ACA) composite were prepared by carbonization and activation of melamine resin and melamine resin/carbon aerogel composite. These were characterized by SEM, XPS, nitrogen adsorption/desorption and electrochemical measurements. Findings indicated than the materials had a highly porous nanometer-sized honeycomb structure and high specific surface area. ANC and ANC/ACA contained 2.22% and 2.12% nitrogen, respectively. The introduction of activated carbon aerogel (ACA) with high conductivity improved the conductivity of ANC. Compared to ACA, greater specific capacitance was obtained for both ANC and ANC/ACA. Asymmetric supercapacitors were assembled with Ni(OH) 2/Co(OH) 2 as anode and our ANC or novel ANC/ACA as cathodes. Electrochemical properties of the supercapacitors with different mass ratios of the two electrodes at different current densities were measured by a galvanostatic charge/discharge technique. When the mass ratio of cathode to anode was 2.2:1 and the current density was 7.5 mA cm −2, the specific capacitance and specific energy of the asymmetric supercapacitor with ANC/ACA as cathode were 110.60 F g −1 and 17.28 Wh kg −1, higher that those of asymmetric supercapacitors with ANC or ACA as cathodes. For ANC/ACA, the attenuation ratio of specific capacitance was only 8.39% after 10,000 cycles. ANC/ACA was found to be a suitable cathode material for use in supercapacitors.