Advanced Supercapacitor Electrodes Research Articles

Anchoring ultrafine Co3O4 grains on reduced oxide graphene by dual-template nanocasting strategy for high-energy solid state supercapacitor

Co3O4-based materials are regarded as superior electrode candidates in various energy storage devices due to their high theoretical capacity. Unfortunately, the poor electronic conductivity and huge volume expansion hamper their widespread applications. Therefore, nano-processing and introducing conductive matrix can view as the necessary methods to make Co3O4-based materials better for an advanced supercapacitor electrode. Herein, a dual-template nanocasting technique is proposed to design the ultrafine Co3O4 grains highly-dispersed on the reduced oxide graphene nanosheets (Co3O4/rGO-C), in which cetyltrimethyl ammonium bromide and silicate species are hired as the ideal soft and hard template, respectively. Co3O4 grains with size <10 nm can expose more active sites and thus exert more redox activities to enhance the capacitive performance. In additional, ∼4 nm moderate pores are obtained in Co3O4/rGO-C after the hard template removing, which provides more diffusion channels for ion/electron rapid transport and also effectively alleviates the volume expansion on cycling. Consequently, the Co3O4/rGO-C electrode exhibits a remarkable specific capacitance (709.1 F g−1 at 1 A g−1) and long-term endurance (91.2% after 6000 cycles). Furthermore, an assembled solid-state asymmetric device of Co3O4/rGO-C||rGO delivers a super-high energy-density of 48.2 Wh kg−1 at 750.5 W kg−1. The high energy-density assists two devices in lightning a red light-emitting diode for 340 s. These results evidence the nanocasting strategy as an efficient method to achieve the advanced electrode materials for energy storage devices.

Enhanced Electrochemical Performance of Cooper Sulfides Coated Electrochemical Modified Carbon Cloth and Its Application in Flexible Supercapacitors

All High-performance flexible electrochemical energy storage devices such as supercapacitors (SCs) and lithium ion batteries (LIBs) are highly desirable as a result of the ever-increasing demands for stretchable electronics. In this work, an effective two-step strategy contain surface and structural modulation and hydrothermal method is developed to grow cooper sulfides onto a highly active surface with pores and numerous functional oxygenic groups. Arising from rough surface and increased active sites, the as-prepared activated loosen cooper sulfides coated electrochemical modified carbon cloths (CuS@ECC) electrode not only achieves a large capacitance (410 F cm−2 at 1 mA cm−2) and fast kinetics but also shows excellent cycling durability (maintain 95% initial capacitance after 3000 cycles). This dual modification strategy may throw light on the rational design of new generation advanced composited electrodes for high-performance flexible supercapacitors.

NiCoSe2/Ni3Se2 lamella arrays grown on N-doped graphene nanotubes with ultrahigh-rate capability and long-term cycling for asymmetric supercapacitor

In this paper, we report a one-step electrodeposited synthesis strategy for directly growing NiCoSe2/Ni3Se2 lamella arrays (LAs) on N-doped graphene nanotubes (N-GNTs) as advanced free-standing positive electrode for asymmetric supercapacitors. Benefiting from the synergetic contribution between the distinctive electroactive materials and the skeletons, the as-constructed N-GNTs@NiCoSe2/Ni3-Se2 LAs present a specific capacitance of ~1308 F g−1 at a current density of 1 A g−1. More importantly, the hybrid electrode also reveals excellent rate capability (~1000 F g−1 even at 100 A g−1) and appealing cycling performance (~103.2% of capacitance retention over 10,000 cycles). Furthermore, an asymmetric supercapacitor is fabricated by using the obtained N-GNTs@NiCoSe2/Ni3Se2 LAs and active carbon (AC) as the positive and negative electrodes respectively, which holds a high energy density of 42.8 W h kg−1 at 2.6 kW kg−1, and superior cycling stability of ~94.4% retention over 10,000 cycles. Accordingly, our fabrication technique and new insight herein can both widen design strategy of multicomponent composite electrode materials and promote the practical applications of the latest emerging transition metal selenides in next-generation high-performance supercapacitors.

One-step hydrothermal synthesis of NiCo2S4 nanoplates/nitrogen-doped mesoporous carbon composites as advanced electrodes for asymmetric supercapacitors

NiCo2S4 nanoplates grow on nitrogen-doped mesoporous carbon (N-MC) are successfully synthesized through a facile one-step hydrothermal method. Study on the synergistic effect of NiCo2S4 and N-MC substrate on the electrochemical properties of composites. The NiCo2S4/N-MC composites electrode exhibits large specific capacitance of 1777 F g−1 at 8 A g−1, excellent rate capability, and an ultralong cycle life (94.20% retention after 3000 cycles at 10 A g−1), which is higher than the pure NiCo2S4. The N-MC substrate has a large specific surface area (126.7 m2 g−1), which can serve as a channel for electrolyte ions and electrons, promote reaction kinetics, and shorten the diffusion distance in redox reaction, thereby improving the performance of pure NiCo2S4. Additionally, the as-synthesized asymmetric supercapacitors based on NiCo2S4/N-MC//N-MC electrodes can be delivered a maximum energy density of 78 W h kg−1 at 4000 W kg−1 and stable cycling stability (91.30% after 5000 cycles). The results demonstrate that the hierarchical NiCo2S4/N-MC composites have great potential applications in energy storage.

NiCo2S4 nanosheet-modified hollow Cu-Co-O nanocomposites as asymmetric supercapacitor advanced electrodes with excellent performance

In this study, hollow CuCo2O4/CuO nanocomposites were fabricated by a hydrothermal method for the first time. NiCo2S4 nanosheets were coated on these nanocomposites by simple potentiostatic electrodeposition to form NiCo2S4 nanosheet-modified hollow CuCo2O4/CuO nanocomposites as advanced electrodes for asymmetric supercapacitors. A unique three-dimensional (3D) nanoarchitecture was built using one-dimensional (1D) hollow CuCo2O4/CuO nanocomposites and two-dimensional (2D) NiCo2S4 nanosheets. This multidimensional synergistic effect resulted in hollow CuCo2O4/CuO@NiCo2S4 nanocomposites with high areal capacitance (10.33 F cm−2, 2459 F g−1) at 10 mA cm−2, good rate capability, and high stability (93.2% retention after 10,000 cycles). Moreover, an environmentally friendly and economical asymmetric supercapacitor was prepared by using hollow CuCo2O4/CuO@NiCo2S4 nanocomposites and activated carbon (AC) as positive and negative electrodes, respectively. This assembly displayed a high energy density of 0.824 mWh cm−2 at a power density of 8 mW cm−2, and 91.2% of the specific capacitance was preserved after 10,000 cycles at 20 mA cm−2. The novel electrode material with a coordinative nanostructure prepared herein provides new possibilities for fabricating high-performance supercapacitors.

Functional molecules regulated and intercalated nickel-cobalt LDH nano-sheets on carbon fiber cloths as an advanced free-standing electrode for high-performance asymmetric supercapacitors

With the aim to enhance the performance of pseudo-capacitor electrode materials, a novel free-standing hybrid electrode through integrating vertically aligned sodium dodecyl benzene sulfonate (SDBS) intercalated NiCo LDH nanosheets and carbon fiber cloth (CFC) was synthesized via a one-step hydrothermal method. The SDBS could serve as NiCo LDH growth regulator and interlayer distance expander. Upon SDBS intercalation the LDH interlayer space increase from 0.79 nm to 1.52 nm, the enlarged interspace could significantly facilitate the ion transportation and boost the specific electrochemical performance. Moreover, the as-prepared NiCo-SDBS-LDH@CFC hybrid material delivers an excellent specific capacity of 748.2 C g−1 at 0.5 A g−1 and outstanding rate capacity of 78.9% at 10 A g−1. Contributed by the delicately engineered electrodes, a high performance of asymmetric supercapacitor (ASC) is constructed, which exhibited a high energy density of 70.94 Wh kg−1 at a power density of 400 W kg−1, the energy density can still remain as high as 59.11 Wh kg−1 at a high power density of 8000 W kg−1. Furthermore, the ACS cell manifests a long lifespan of 89.96% capacitance retention at 10 A g−1 even after 10000 cycles. This work not only demonstrates an attractive strategy for rational design and modification of LDH-based electrodes, but also provides superior nanostructured free-standing electrodes for high energy density supercapacitors.

One-pot scalable synthesis of pure phase Ni3S4 quantum dots as a versatile electrode for high performance hybrid supercapacitors and lithium ion batteries

Transition metal based quantum dots (QDs) have great potential for electrode materials of advanced electrochemical energy storage due to their unique structural superiorities. Here, we develop a simple, green and scalable one-pot method for the synthesis of 10-g-scale monodisperse nickel sulfides QDs. Interestingly, the composition of the target QDs products can be precisely regulated through adjustment of the concentration of 6-mercapto-1-hexanol ligands in precursor solution and thus pure phase Ni3S4 QDs are obtained. Benefiting from the advantages of high specific area carrying more metallic active sites and rich pore structure in favor of the diffusion of electrolyte ions, the optimal Ni3S4 QDs manifest extraordinary electrochemical performance as advanced electrodes for both hybrid supercapacitors and lithium ion batteries. Impressively, the constructed hybrid supercapacitor achieves high energy density of 49.3 Wh·kg−1 and power density of 21718 W kg−1 with a robust stability of maintaining 91.7% after 8000 cycles. When applied to anode materials of lithium energy storage, Ni3S4 QDs can deliver a high reversible specific capacity of 647.5 mAh·g−1 at 100 mA g−1 with remarkable cyclic performance of losing only 2% reversible capacity value under 500 cycles.

Nitrogen-containing graphene networks with high volumetric capacitance and exceptional rate capability

Graphene has attracted more attention as advanced electrodes for supercapacitors due to its unique geometry structure and outstanding physicochemical property. But its low specific capacitance, especially low volumetric capacitance, has greatly restricted the practical application of graphene electrode materials. Herein, we synthesized nitrogen-containing graphene networks by using 2, 3-diaminopyridine (O-DAP) as functional agent in a facile hydrothermal route. During the hydrothermal process, not only the pyrrolic-N, but also the pyrazine-N is produced in the graphene lattice at the edge/defect site of graphene because of the double –NH2 in DAP reactant. Owing to the high nitrogen content (17.5 at%), special nitrogen configuration, and high density (1.66 g cm−3), the N-containing graphene networks present high gravimetric capacitances up to 353 F g−1 and high volumetric capacitances over 586 F cm−3 in 1 M H2SO4 electrolyte. More remarkably, the N-containing graphene electrodes exhibit exceptional rate capability with a capacitance retention of 80.6% at a high current density of 20 A g−1 and good cycling stability of 91.5% retention after 5000 cycles in a symmetrical two-electrode configuration.

Progress Report on Atomic Layer Deposition Toward Hybrid Nanocomposite Electrodes for Next Generation Supercapacitors

AbstractIn present supercapacitors' research atomic layer deposition (ALD) has proven to be a better technique of choice since the controlled deposition and better conformal surface coating minimize the ion diffusion and charge transport path which result in a supercapacitor with optimized energy and power density, good cyclic stability, and rate capability. This progress report summarizes the recent advances in ALD toward fabrication and surface modification of advanced hybrid nanocomposite electrodes for supercapacitors using some selected examples. A particular emphasis is given to the key role of ALD parameters in influencing the electrochemical performance of hybrid nanocomposite. In addition, the authors point out the current challenges and the strategies for future fine utilization of this technique to achieve desired energy density and overall performance. The authors anticipate this report to provide some insights and motivations to design high performance next generation supercapacitors by manipulating the parameters of ALD when using various active materials.

In-situ activation endows the integrated Fe3C/Fe@nitrogen-doped carbon hybrids with enhanced pseudocapacitance for electrochemical energy storage

Limited energy density of carbon material stimulates the further development of other advanced negative electrodes for supercapacitors. Herein, a facile strategy is presented for the fabrication of nitrogen-doped carbon matrix encapsulated with the Fe3C/Fe nanoparticles core-shell architectures. The obtained hybrid is constructed by interwoven carbon nanosheets, pod-like carbon nanotubes and Fe3C/Fe nanoparticles, yielding integrated porous conductive networks. Interestingly, after fifteen cyclic voltammetry cycles, the Fe3C/Fe@NC as negative electrode exhibits a much enhanced pseudocapacitance of 1695 F g−1 at 2 A g−1. The in-depth analyses indicate that a dominant Fe3O4 phase with new morphology is formed during the electrochemical activation processes. Thus, the authentic active species accounted for the Faradaic redox reactions should be the Fe3O4, rather than the Fe3C/Fe itself. Furthermore, the assembled asymmetric supercapacitor with Fe3C/Fe@NC as the anode and Ni(OH)2 as the cathode delivers a high energy density of 72 Wh kg−1 at a power density of 0.83 kW kg−1 and a long cycling life, which is superior to those of other reported iron-based materials. This work not only provides a simple in situ activation approach to realize the utilization of Fe3C/Fe, but also paves an avenue for developing advanced negative materials for supercapacitors.

Ethanol interfacial assembly of Na0.44MnO2 nanorod/active carbon toward the fabrication of high-density hybrid films for binder-free supercapacitor electrode

There is an intense interest for utilization of self-assembly to fabricate high-density hybrid films for practical energy storage. In this paper, high-density (1.5 mg/cm2) hybrid Na0.44MnO2 nanorod (average diameter 70 nm and average aspect ratio 10)/active carbon films (with area of 9 cm2) were fabricated by direct toluene/water interfacial assembly, achieving the binder-free supercapacitor electrode with advanced electrochemical performance. The density of interfacial films can be precisely controlled by regulating the dosage of assembled nano-units. We showed that the hybrid films can be easily transferred onto a Ni foam and subsequently use as binder-free supercapacitor electrode. The electrochemical testing of film electrode exhibited a high specific capacitance of 189.6 F/g and good capacitance retention at high charge-discharge rates as well as cycling stability. It is suggested that this direct interfacial assembly approach paves the way for the fabrication of 2D functional nanomaterials, particularly useful in practical applications, such as advanced supercapacitor electrode.

Hierarchical Fe2O3 and NiO nanotube arrays as advanced anode and cathode electrodes for high-performance asymmetric supercapacitors

Rational design and fabrication of advanced electrodes with tailored functionality is of great significance for high-performance asymmetric supercapacitors. Herein, we report the preparation of Fe2O3 nanotube arrays and core-branch NiO nanotube arrays directly on carbon paper by using ZnO nanorods as sacrificial templates via similar synthesis process, which works anode and cathode electrodes for the asymmetric supercapacitors. Benefiting from the free-standing nanotube nanostructures, a large number of surface active sites and fast ion diffusion paths, the Fe2O3 and NiO electrodes could achieve the high capacity up to 81.9 mAh g−1 and 119.7 mAh g−1, respectively. Further, an asymmetric supercapacitor is also assembled by using Fe2O3 as anode and NiO as cathode, which shows a high energy density of 48 Wh kg−1 at the power density of 2089 W kg−1. Current research may put a general route for constructing high-performance anode and cathode materials in energy storage devices.

Controllable synthesis of CoNb2O6 nanoparticles on multifunctional sulfur and phosphorus dual-doped graphene as advanced electrodes for hybrid supercapacitors

Battery type hybrid supercapacitors have drawn more attention as a great potential storage device with both excellent rate capability and high energy densities. Herein, we demonstrate a facile hydrothermal method to the preparation of sulfur and phosphorus atoms co-doping into the graphene nanosheet (SPG) using sulphuric acid and phytic acid as dopant. The NbCo precursor could be uniformly dispersed in SPG by formation of coordination bonds with the six phosphate groups of phytic acid. Morphological characteristic indicate that the CoNb2O6 nanoparticles grown directly on three-dimensional SPG framework (CoNb2O6/SPG) through high temperature calcination. As battery-type hybrid supercapacitors equipment, the asymmetric device consisting of CoNb2O6/SPG hybrids and active carbon (AC) delivers remarkable cycling stability (92.5% of the initial after 10,000 charge and discharge cycles) and outstanding rate capability (73.9% retention from 0.5 to 4 A g−1). More remarkably, the above device exhibits an impressive energy density of 39.7 Wh kg−1 at a high power density of 2995 Wkg-1. This outstanding performance is mainly ascribed to the large surface area and highly conductive of S and P co-doped 3D graphene architecture, the uniformly distributed and highly exposed CoNb2O6 nanoparticles and the incorporating effects with them.

Morphology-controllable synthesis of CuCo2O4 arrays on Ni foam as advanced electrodes for supercapacitors

The rational design of novel electrode materials with controllable morphologies plays a vital role in fabricating high-performance supercapacitors. In this work, a variety of CuCo2O4 arrays with different components (nanoneedle, nanosheet and nanorod) on nickel foam have been synthesized through facile hydrothermal routes. The key roles of NH4F and the alkali sources in the formation of different CuCo2O4 arrays have been discussed. As a three-electrode cell, the Ni supported CuCo2O4 nanoneedle arrays exhibit a specific capacitance of 1227.8 F g−1 at 5 mA cm−2 and capacitance retention of 95.4% after 1000 cycles, suggesting the potential application for supercapacitors. Furthermore, an asymmetric supercapacitor is fabricated with CuCo2O4 nanoneedle arrays (the anode) and activated carbon (AC) electrode (the cathode), which achieves a high energy density (31.2 W h kg−1) and excellent cycling stability (102% after 4000 cycles). Such remarkable performance is ascribed to the favorable porous structure of CuCo2O4 nanoneedle arrays which can offer abundant channels for ion diffusion and numerous active spots for reversible redox reactions. It is hoped that our work could provide inspirations for the morphology-controllable fabrications of electrode materials.

From interpenetrating polymer networks to hierarchical porous carbons for advanced supercapacitor electrodes

Hierarchical porous carbons (HPCs) are obtained via in-situ activation of interpenetrating polymer networks (IPNs) obtained from simultaneous polymerization of resorcinol/formaldehyde (R/F) and polyacrylamide (PAM). The hierarchically micro-, meso- and macroporous structure of as-prepared HPCs is attributed to the synergistic pore-forming effect of PAM and KOH, including PAM decomposition, KOH chemical activation, and a foaming process of potassium polyacrylate formed by partial hydrolysis of PAM in KOH aqueous solution. The typical HPC electrode with the highest surface area (2544 m2/g) shows a high specific capacitance of 261 F/g at 1.0 A/g and a superior rate capability of 216 F/g at 20 A/g in alkaline electrolyte. Moreover, the electrode maintains the capacitance retention of 90.8% after 10000 charging-discharging cycles at 1.0 A/g, exhibiting long cycling life. This study highlights a new avenue towards IPNs-derived carbons with unique pore structure for promising electrochemical applications.

The template effect of silica in rice husk for efficient synthesis of the activated carbon based electrode material

Development of the synthesis methods of rice husk-based activated carbon (AC) as electrode materials by utilizing the natural silica template effect has been of special interests for high quality electrode material design. To enhance the silica template efficiency, a selective leaching out of the useless silica exposed on sample surface using NaOH solution at a moderate condition was adopted. The actual silica template located within the sample could be preserved and work with alkali activators to open the firm carbon texture, offer more active sites for pore generation, and therefore could improve the specific capacitance. The electrochemical performance of the prepared AC products was thoroughly characterized and a high specific capacitance together with extraordinary cycling stability was observed. This strategy offered an applicable way to facilitate industrial synthesis of high quality AC based electrodes for advanced supercapacitors.

Design of the seamless integrated C@NiMn-OH-Ni3S2/Ni foam advanced electrode for supercapacitors

Rational design and fabrication of hierarchical structures consisting of multiple components with distinctive features in situ grown on porous Ni foam skeleton is feasible and effective to boost the electrochemical properties of supercapacitors. Herein, a novel hierarchical C@NiMn-OH-Ni3S2/Ni foam hybrid integrated advanced electrode was successfully fabricated via a facile three-step hydrothermal method, involving two hydrothermal reaction to grow NiMn-OH nanoflakes onto Ni3S2 thin film in situ grown on conductive Ni foam and then a glucose carbonization process to cover carbon on NiMn-OH. Benefiting from the synergistic effect of Ni3S2 and NiMn-OH with enhancement of both the electrical and the ionic conductivity, the as-obtained C@NiMn-OH-Ni3S2/Ni foam exhibited an excellent specific capacitance of 2521 F g−1 at a current density of 1 A g−1, and cycle stability increased from 82.4% to 92.1% after coating the carbon layer. Furthermore, an aqueous asymmetric supercapacitor was successfully assembled using C@NiMn-OH-Ni3S2/Ni foam as the positive electrode and activated carbon (AC) as the negative electrode (C@NiMn-OH-Ni3S2/Ni foam//AC), such device delivers a maximum energy density of 45.3 Wh kg−1 at the power density of 1275 W kg−1, and a superior cycling stability (∼94.6% capacity retention after 10,000 cycles).

Controlled synthesis of unique Co9S8 nanostructures with carbon coating as advanced electrode for solid-state asymmetric supercapacitors

Stimulated by both the rich electrochemical properties and unique structural merits, much attention is directed to construct novel cobalt sulfides nanoarchitectures for energy storage devices. Here, carbon-coated cobalt sulfide nanostructures are fabricated with the assistance of polyvinylpyrrolidone during hydrothermal process. The morphology of carbon-coated cobalt sulfide can evolve from well-defined uniform nanooctahedrons, nanoflowers to nanospheres by simply controlling the polyvinylpyrrolidone amount. Remarkably, the unique carbon-coated cobalt sulfide configuration takes full advantage of the synergistic contributions from both the homogeneous incorporated carbon layer and the ideal hierarchical flowerlike structures, thereby making it to be a suitable electrode for supercapacitors. By virtue of the intriguing structural features of carbon-coated cobalt sulfide, a solid asymmetric supercapacitor based on carbon-coated cobalt sulfide nanoflowers as the positive electrode and active carbon as the negative electrode achieves remarkable cycling stability (around 86% capacitance retention even up to 10,000 times), and outstanding energy density of 40 Wh kg−1 at power density of 850 W kg−1. The exceptionably electrochemical performance of the asymmetric supercapacitor is related to the enhanced electrical conductivity and increased electrode/electrolyte contact area of carbon-coated cobalt sulfide. Thus, the as-prepared carbon-coated cobalt sulfide nanoflowers is demonstrated to be a promising electrode for asymmetric supercapacitors.

Design of Mo-doped cobalt sulfide hollow nanocages from zeolitic imidazolate frameworks as advanced electrodes for supercapacitors

A Mo-doped CoS HNC with enhanced electrochemical performance was designed by using ZIF-67 as a self-sacrificial template through a dissolution–regrowth process in the presence of NaMoO4with an additional sulfurization process.

Bi2S3 nanorod-stacked hollow microtubes self-assembled from bismuth-based metal-organic frameworks as advanced negative electrodes for hybrid supercapacitors.

Bismuth sulfide (Bi2S3) with a lamellar structure has emerged as a promising negative electrode material for supercapacitors (SCs) due to its high theoretical specific capacity. Meanwhile, the improvement of electrochemical properties strongly depends on the size, shape and morphologies of Bi2S3 nanomaterials. Herein, the hierarchical Bi2S3 nanorod-stacked hollow microtubes are self-assembled through a facile self-sacrificing template strategy from bismuth-based metal-organic framework microprisms. Benefiting from the unique structures with a large specific surface area (54.3 m2 g-1), the as-prepared Bi2S3 exhibits an ultrahigh specific capacity (532 C g-1 at 1 A g-1) as a negative electrode for SCs, outperforming other reported Bi2S3 materials.