Electrodes For High-performance Asymmetric Supercapacitors Research Articles

Construction of hierarchical and core-shell structured Co3O4@MnO2@NiO nanoarrays as binder-free electrodes for high-performance asymmetric supercapacitors

Remarkable specific capacity and excellent cycle stability of the electrode materials are vital prerequisites for their practical applications. Transition metal oxide-based materials have been extensively explored and employed as electrode materials for asymmetric supercapacitors. However, the actual specific capacitances of these materials are still far lower than their theoretically predicted values. Thus, it is essential to design transition metal oxide with novel structures in order to maximize their specific capacity and cycle stability. Herein, we constructs hierarchical and core-shell structured Co3O4@MnO2@NiO arrays on nickel foam (Co3O4@MnO2@NiO/NF) through a three-step hydrothermal-annealing process, and use them as a direct binder-free electrode for pseudocapacitors. The as-prepared layered hierarchical Co3O4@MnO2@NiO/NF electrode exhibits an impressive specific capacitance of 6.42 F cm−2 (2054 F g−1) at 1 mA cm−2 in a three-electrode configuration, which is largely because of the synergistic effect among Co3O4, MnO2 and NiO. Furthermore, the 3D nanoarray structure can provides a larger specific surface area, a rapid diffusion path, and more active sites that allow to achieve improved electrochemical performance. In addition, the assembled Co3O4@MnO2@NiO/NF//AC/NF ASC all-solid-state asymmetric supercapacitor (ASC) displays a remarkable energy density (30.7 Wh kg−1 at 400.4 W kg−1), demonstrating that this all-solid-state ASC owns considerable potential for practical applications in such high-performance energy storage devices.

Facile synthesis of MWCNT hexagonal needles grown on interconnected honeycombs like MnCo2O4/MnO2 nanoporous electrode for high-performance asymmetric supercapacitor

The construction of a honeycomb-like structure composed of MnCo2O4/MnO2was effectively achieved using a combination of hydrothermal processing and heat treatment. The whole surface of the MnCo2O4/MnO2 honeycomb is coated with neatly arranged hexagonal nano needles made of MWCNT, leading to a substantial enhancement in the specific surface area. At 1 A/g, the supercapacitor electrode composed of MnCo2O4/MnO2@MWCNT composite exhibited an exceptional specific capacitance of around 1539 F/g. Furthermore, it maintained approximately 95.5 % of its capacity even after undergoing 10,000 cycles. The asymmetric capacitor device, with MnCo2O4/MnO2@MWCNT and AC electrode, has a power density of 1537.8 W kg−1 and an energy density of 48.78 Wh kg−1. The MnCo2O4/MnO2composite exhibits exceptional rate performance, significant capacitance, and excellent cycle performance due to the synergistic effect between MnCo2O4/MnO2 and MWCNT, as well as the high specific surface area and unique structure. Consequently, it presents a viable option for the advancement of high-efficiency electrochemical super capacitors in the next generation.

Controlled preparation of carbon cloth decorated with nanostructured Mn(OH)2/Mn3O4 electrodes for high-performance asymmetric supercapacitors

Environmentally friendly aqueous asymmetric supercapacitors are expected to exhibit excellent energy storage properties, stable performance, and facile production protocols. This study focused on the fabrication and characterisation of an asymmetric supercapacitor (ASC) with a commercial activated carbon (AC) negative electrode and Mn(OH)2/Mn3O4 composite on carbon cloth (hCC) positive electrode. The Mn-based electrode was synthesised using a one-step electrodeposition process. The morphology and crystalline structure of the composite electrode were modified by varying the deposition time of the Mn(OH)2/Mn3O4 nanostructures on carbon cloth substrate which greatly influence the electrochemical performance of the asymmetric systems. The best ASC used the AC electrode and a Mn(OH)2/Mn3O4@hCC electrode prepared using electrodeposition over an optimised time of 3 h. It exhibited a remarkable specific energy density of 40.7 Wh kg−1 at a power density of 100 W kg−1. In addition, this ASC demonstrated stable long-term performance, retaining 88 % of its capacitance after 5000 charge–discharge cycles, showing its great application potential in the field of supercapacitors.

3D Architecting triple gradient graphene-based fiber electrode for high-performance asymmetric supercapacitors

High-performance fibrous architectures and controllable fabrication methods for active nanomaterials are fundamental in the development of fiber-based supercapacitors (FSCs). Herein, we rationally designed a triple gradient structured fibrous electrode based on three-dimensional (3D) architectural approach with Ni3S2 nanoflakes (Ni3S2 NFs) in situ growth on Ni-coated graphene fiber (Ni3S2-NiGFs) for highly energy-dense asymmetric supercapacitors. Remarkably, the Ni-metal coating imparted the Ni3S2-NiGFs exceptional electrical conductivity (619.8 S cm−1), mechanical strength (335.0 MPa), and flexibility without significantly compromising its density. Moreover, the unique 3D interconnected ultrathin Ni3S2 NFs significantly increase the contact area between the electrode and the electrolyte solution, providing abundant redox activity to facilitate ion transport and accumulation. Therefore, the fibrous electrode showcased a remarkable areal specific capacitance of 1387.6 mF cm−2 at 3 mA cm−2 in 3 M KOHaq electrolyte, while its asymmetric FSCs delivered an impressive areal energy density of 15.6 μW h cm−2 at power density of 1.0 mW cm−2 along with durable cycle life (86.7 % of the initial specific capacitance retention over 10,000 cycles). In summary, the featured work provides a facile but robust electrode design to realize highly energy-dense flexible energy storage devices for next-generation wearable industries.

Optimized 3D interconnected foam-like NiO@rGO composite as a binder-free electrode for high-performance asymmetric supercapacitor

Bonding of transition metal oxides and highly conductive carbon materials to exploit the synergistic effect of both materials has been proven to be an efficient means to develop high-capacity electrode materials. A unique interconnected foam-like NiO@rGO structure was constructed by loading the NiO nanoparticles onto rGO frameworks as a binder-free supercapacitor electrode via three steps including hydrothermal reaction, electrodeposition and heating treatment. The morphology and crystallinity were tuned by controlling the electrodeposition time and heating temperature, and the electrochemical properties of the NiO@rGO composites were systematically investigated. The optimized NiO@rGO-250 composite showed excellent electrochemical properties (1399 F g−1 at 1 A g−1) and superior cycling stability. Furthermore, an asymmetric supercapacitor using NiO@rGO and active carbon as two electrodes achieved a high specific energy of 40.4 Wh k g−1 at a specific power of 750 W k g−1.

Controllable synthesis of MnSe2/Co0.85Se nanosheets as a binder-free electrode for high-performance asymmetric supercapacitors

With the increasingly serious environmental pollution and depletion of natural resources, it is necessary to develop efficient and environmentally friendly energy storage equipments to alleviate the problem of resource shortage. In this study, a novel MnSe2/Co0.85Se (MCSe) electrode was successfully prepared using a simple, green and environmentally friendly electrodeposition method. The MCSe electrode exhibited good electrochemical performance, and possesses a high specific capacity (Cs) of 1380C/g at a current density (CD) of 1 A/g. An asymmetric supercapacitor (ASC) assembled using a positive electrode (the MCSe electrode) and a negative electrode (active carbon (AC) electrode) delivered a high specific energy density (Es) of 49.63 Wh/kg at a specific power density (Ps) of 750 W/kg. Hence, this study provides a new approach for designing metal selenides for energy storage and conversion.

Novel 2D CeO2 nanoflakes as a high-performance asymmetric supercapacitor electrode material

Enhancing the performance and durability of benchmarked metal catalysts using nanostructured non-metallic materials is an active area of research that is exciting from both a fundamental and an application perspective. The 2D CeO2 nanoflakes are characterized using structural and electrochemical techniques. Galvanostatic charge-discharge (GCD) revealed that the material delivers a specific capacitance of 1801 F/g at 1 A/g, among the best-reported values for transition and rare earth metal oxide electrode material. Due to its nanoflake-like structure, the sample has a modest surface area (12.6 m2/g). Asymmetric supercapacitor device (CeO2//AC) fabricated delivered an energy density of 57.6 Wh/kg and a power density of 771 W/kg with 83 % capacitance retention after 1000 cycles in 3 M KOH. This study reveals that CeO2 is a promising electrode material for energy storage applications.

Three-dimensional FeNiP decorated graphene sponge: A novel flexible electrode for high-performance asymmetric supercapacitor

Here, a three-dimensional (3D) flexible material was prepared based on FeNiP decorated graphene sponge (GrS) by a two-step method. Free-standing 3D GrS was fabricated through a simple foaming-drying method, then FeNiP was electrodeposited onto flexible GrS material to achieve a flexible FeNiP/GrS sponge electrode for high-performance electrochemical supercapacitors. This composite material exhibited a high specific capacitance of 2292 F/g and 90% of the specific capacitance was retained after 10,000 charge/discharge cycles at a current density of 1 A/g. An asymmetric supercapacitor (FeNiP/GrS//GrS) was fabricated and this flexible circuit delivered a maximum power density of 6545 W/kg and a high energy density of 330 Wh/kg. This outstanding electrochemical performance could be attributed to the high charge conductivity of FeNiP and porous graphene sponge which provides good structure stability, large reaction surface area, and high electron transfer.

Carbon nitride mediated synthesis of titanium-based electrodes for high-performance asymmetric supercapacitors

Rational design of electrode materials with specific compositions and unique morphological and structural features to achieve supercapacitors (SCs) with high energy densities without compromising their inherent electrochemical merits remains a great challenge. Herein, a carbon nitride (C3N4) mediated “one-for-two” strategy was proposed to synthesize titanium nitride/carbon nanosheets (TiN/C) and titanium carbide/carbon nanosheets (TiC/C) with three-dimensional morphology and hierarchical structure, respectively. The derived TiN/C and TiC/C were used as cathode and anode materials, respectively, with excellent capacitor behavior in aqueous electrolyte. Specifically, asymmetric SCs constructed with the TiN/C cathode and the TiC/C anode delivered a large operation voltage of 0.3–1.8 V, a high specific capacitance of 103 F·g−1, and a remarkable energy density of 45.2 Wh·kg−1, outperforming most of the previously reported TiN- and TiC-based SCs. Ex situ XRD and TEM characterizations as well as DFT simulation indicated that the excellent performance could be attributed to reversible pseudocapacitive redox reaction and electro-adsorbed anions at the TiN/C cathode, and fast adsorption/desorption of cations at the TiC/C anode, as well as unique surface morphology and heterostructure. The strategy presented in this work also provides new design concepts for the synthesis of other transition metal nitrides (or carbides)/carbon composites for other advanced energy applications.

A Cobalt-Based Metal-Organic Framework Nanosheet as the Electrode for High-Performance Asymmetric Supercapacitor.

Inspired by the significant advantages of the bottom-up synthesis whose structures and functionalities can be customized by the selection of molecular components, a 2D metal-organic framework (MOF) nanosheet Co-BTB-LB has been synthesized by a liquid-liquid interface-assisted method. The as-prepared Co-BTB-LB is identified by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDX) and X-ray photoelectron spectroscopy (XPS), and the sheet-like structure is verified by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM). Co-BTB-LB electrode exhibits an excellent capacity of 4969.3Fg-1 at 1Ag-1 and good cycling stability with 75% capacity retention after 1000 cycles. The asymmetric supercapacitor device with Co-BTB-LB as the positive electrode shows a maximum energy density of 150.2Whkg-1 at a power density of 1619.2Wkg-1 and good cycling stability with a capacitance retention of 97.1% after 10000 cycles. This represents a state-of-the-art performance reported for asymmetric supercapacitor device using electroactive bottom-up metal-complex nanosheet, which will clearly lead to a significant expansion of the applicability of this type of 2D nanomaterials.

One-pot synthesis of flower-like Ni-Co/reduced graphene oxide layered double hydroxide nanocomposites as advanced electrodes for high-performance asymmetric supercapacitors

Novel electrode materials with appropriate architectures are always desired to increase the energy density of supercapacitors. Here, the design and fabrication of NiCo-layered double hydroxides (NC-LDH) in composition with reduced graphene oxide (rGO) were prepared as high-performance electrodes for supercapacitors. In particular, a facile and one-pot scheme was designed for the growth of NC/rGO-LDH composites, which exhibited a high specific surface area of 204 m2/g. The compositional features of the composites, i.e., a two-dimensional flower-like layered architecture and conductive rGO, contributed to their highly impressive specific capacitance (1913.5 F/g at 1 A/g) and excellent cyclic performance. Furthermore, an asymmetric supercapacitor was designed using NC/rGO-LDH composites as the positive electrode and activated carbon as the negative electrode, which displayed a high energy density of 59.2 Wh/kg at a power density of 750 W/kg.

Preparation of rGO/MXene@NiCo-P and rGO/MXene@Fe2O3 positive and negative composite electrodes for high-performance asymmetric supercapacitors

In this study, reduced graphene oxide/MXene-based composite electrodes combined with Fe2O3 and NiCo-P as the negative and positive electrodes are prepared by a facile in-situ solvothermal route. Both rGO/MXene@Fe2O3 and rGO/MXene@NiCo-P have an interconnected nanostructure with the specific surface areas at 17.1 and 131.9 m2·g−1. The specific capacitance of the as-prepared rGO/MXene@Fe2O3 and rGO/MXene@NiCo-P composite electrodes are 248.13 and 214.66 mAh·g−1 under current density at 1 A·g−1. An asymmetric supercapacitor (ASC) is further assembled using rGO/MXene@Fe2O3 and rGO/MXene@NiCo-P as the negative and positive electrodes, respectively. The maximum energy density of the assembled ASC is 29.46 Wh·kg−1 at a power density of 700.34 W·kg−1. After 10,000 cycles, 70.87 % of the capacity can be retained. These results demonstrate the potential application of composite electrode materials for supercapacitors.

MXene/carboxymethylcellulose-polyaniline (Ti3C2Tx/CMC-PANI) film as flexible electrode for high-performance asymmetric supercapacitors

Two-dimensional (2D) MXene (Ti3C2Tx) materials have received widespread attention as potential electrodes for supercapacitors due to their solution processability, metallic conductivity and excellent energy storage properties. Unfortunately, the self-stacking and interlayer interactions of Ti3C2Tx flakes cause them to acquire poor electrochemical characteristics. Herein, the interwoven carboxymethylcellulose-polyaniline (CMC-PANI) composites were prepared by in-situ polymerization of aniline on the surface of CMC, which was subsequently used as the intercalators to expand the layer spacing of Ti3C2Tx nanosheets via a facile self-assembly process. The interwoven CMC-PANI bridges horizontal Ti3C2Tx nanosheets to construct interconnected conductive and ion channels, making the internal structure of the Ti3C2Tx/CMC-PANI (TCP) film more uniformly and orderly, thereby achieving a high mechanical strength (≈ 35.6 MPa). Meanwhile, the TCP film exhibits a maximum area specific capacitance of 1161.4 mF cm−2 (812.9 mC cm−2) at 1 mA cm−2, and a superior rate performance (maintains 58.4% of the initial value at 50 mA cm−2). Moreover, the fabricated asymmetric supercapacitor (ASC) device presents a high area energy density of 158.7 µW h cm−2 at a power density of 700.1 µW cm−2 and good cycle stability (retention of 89.6% after 15,000 charging/discharging cycles). This rational design balancing flexibility and electrochemical performance provides a broadened idea to solve the inherent defects of MXene and further develop high performance energy storage devices.

Inverse spinel cobalt manganese oxide nanosphere materials as an electrode for high-performance asymmetric supercapacitor

In energy storage devices, it is critical to further develop spinel structured functional materials with rich redox-active sites and high theoretical capacitance. In this study, the nanosphere-shaped Cobalt Manganese Oxide inverse spinel structure was prepared by polyvinylpyrrolidone-assisted hydrothermal technique followed by calcination at 300 °C. Benefitting from the small nanosphere architecture, the Cobalt Manganese Oxide exhibits a high specific surface area to offer more redox-active sites and has a highly porous nature to shorten the ion movement pathway. The obtained Cobalt Manganese Oxide nanospheres exhibit a battery-like energy storage mechanism with a specific capacity (580 C g−1 at 5 mV s−1), high rate capability, and long-term cyclic stability performance (91.2% at 100 mV s−1 for 5000 cycles) in 6 M KOH electrolyte. The fabricated asymmetric supercapacitor device displays a high energy density of 29.1 Wh kg−1 at a power density of 320 W kg−1, and a power density of 3840 W kg−1 at an energy density of 4.4 Wh kg−1 with cyclic stability of 96.5% after 10,000 galvanostatic charge/discharge (GCD) cycles. The electronic structural properties explain density functional theory (DFT).

Self-Supported Co3O4@Mo-Co3O4 Needle-like Nanosheet Heterostructured Architectures of Battery-Type Electrodes for High-Performance Asymmetric Supercapacitors.

Herein, this report uses Co3O4 nanoneedles to decorate Mo-Co3O4 nanosheets over Ni foam, which were fabricated by the hydrothermal route, in order to create a supercapacitor material which is compared with its counterparts. The surface morphology of the developed material was investigated through scanning electron microscopy and the structural properties were evaluated using XRD. The charging storage activities of the electrode materials were evaluated mainly by cyclic voltammetry and galvanostatic charge-discharge investigations. In comparison to binary metal oxides, the specific capacities for the composite Co3O4@Mo-Co3O4 nanosheets and Co3O4 nano-needles were calculated to be 814, and 615 C g−1 at a current density of 1 A g−1, respectively. The electrode of the composite Co3O4@Mo-Co3O4 nanosheets displayed superior stability during 4000 cycles, with a capacity of around 90%. The asymmetric Co3O4@Mo-Co3O4//AC device achieved a maximum specific energy of 51.35 Wh Kg−1 and power density of 790 W kg−1. The Co3O4@Mo-Co3O4//AC device capacity decreased by only 12.1% after 4000 long GCD cycles, which is considerably higher than that of similar electrodes. All these results reveal that the Co3O4@Mo-Co3O4 nanocomposite is a very promising electrode material and a stabled supercapacitor.

Composite Assembling of Oxide-Based Optically Transparent Electrodes for High-Performance Asymmetric Supercapacitors.

Simultaneously achieving a transparent and high-energy density supercapacitor is a major challenge because of the trade-off between energy storage capacity and optical transparency of active electrode materials. Herein, we demonstrate a novel approach to construct an optically transparent asymmetric supercapacitor (Trans-ASC) by assembling positive (ZnO-SnO2) and negative (TiO2-SnO2) composite thin-film electrodes on a conductive indium-doped tin oxide substrate via reactive DC magnetron cosputtering. The optical transmittance for both composite thin films is found to be 68% (ZnO-SnO2) and 64% (TiO2-SnO2). Furthermore, electrochemical kinematics of the primed transparent electrodes are scrutinized in 0.5 M KOH electrolyte without affecting the transparency of active electrodes. The structural reliability of the electrodes aids the superb electrochemical performance to construct a Trans-ASC, TiO2-SnO2//ZnO-SnO2, which works at a voltage of +1.2 V and attains a higher areal capacitance of 44.6 mF cm-2 at 2 mA cm-2. The assembled Trans-ASC delivers a maximum areal energy density of 8.75 μW h cm-2 with an optimal areal power density of 570 μW cm-2. Additionally, the capacitance retention of 81.6% and transparency of both electrodes remain almost the same (up to 60% for ZnO-SnO2 and 62% for TiO2-SnO2) even after 10,000 charging-discharging cycles. These remarkable electrochemical properties and outstanding cycling stability of the designed Trans-ASC device make it a potential candidate for storing energy and for further use in transparent electronic devices.

Fe2O3/nitrogen-doped carbon nanotube composites as positive electrode for high-performance asymmetric supercapacitors

Fe2O3/nitrogen-doped carbon nanotube composites as positive electrode for high-performance asymmetric supercapacitors

NiSe2 nanocrystals intercalated rGO sheets as a high-performance asymmetric supercapacitor electrode

There is a growing demand for renewable and sustainable energy conversion and storage devices with the exhaustion of fossil fuels and increasing environmental contamination. In this paper, nickel diselenide (NiSe2) structures wrapped with various rGO (4%, 8%, 16%, and 32%) weight ratios were fabricated using a simple hydrothermal method and their structural, morphological, and electrochemical characteristics were studied systematically. The electrochemical properties of NiSe2/rGO with varying rGO concentrations were studied, and their supercapacitive performance was evaluated. NiSe2-16% rGO electrode outperformed NiSe2-32% rGO, NiSe2-8% rGO, and NiSe2-4% rGO due to its interconnected network topology and decreased effect of volume expansions. Moreover, during electrochemical activities, the optimum NiSe2-16% rGO electrode exhibited a high specific capacitance (1845.5 F g−1 at 1.5 A g−1), excellent cycling stability (99.4% over 5000 cycles), and rapid ion/electron transit. An asymmetric supercapacitor with NiSe2-16% rGO as anode and activated carbon as cathode exhibited a high energy density of 12.66 Wh kg−1 at 3999.84 W kg−1 and 99% retention of capacitance after 8000 repeated cycles. Our results have successfully demonstrated that the fabricated asymmetric supercapacitor has potential applications in the energy storage field.

Facile stepwise hydrothermal synthesis of hierarchical CoMoO4/CoMoO4 core/shell dandelion-like nanoarrays: A promising binder-free positive electrode for high-performance asymmetric supercapacitors

In this study, we have fabricated a flexible supercapacitor with outstanding pseudocapacitive performance using hierarchical CoMoO4/CoMoO4 core/shell dandelion-like nanoarrays. The dandelion-like CoMoO4/CoMoO4 nanostructure electrode yields a high specific capacitance (1548 F g−1 at a current density of 1 A g−1) and superior cycling stability performance (94% capability retention after 5000 cycles at 8 A g−1) in the 3 mol L–1 KOH solution. Furthermore, a flexible asymmetric supercapacitor device was assembled based on nickel foam/CoMoO4/CoMoO4 dandelion-like as positive electrode and activated carbon (AC) as negative electrode. The CoMoO4/CoMoO4 nanostructure//AC asymmetric supercapacitor device represents remarkable electrochemical performance such as good specific capacitance of 152 F g−1 and maximum energy and power densities of 54.04 Wh kg−1 and 8.83 kW kg−1, respectively. These encouraging results depict great potential in developing energy storage devices by making heterostructure nanomaterials.

Facile Synthesis of Flower-Like Bi2o3 as an Efficient Electrode for High-Performance Asymmetric Supercapacitor

Facile Synthesis of Flower-Like Bi2o3 as an Efficient Electrode for High-Performance Asymmetric Supercapacitor