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•FeOOH nanostructures with diatom 3D morphology were fabricated.•Successful transition from MnO2 to FeOOH with diatom replica were confirmed.•High electrochemical performance of FeOOH ...replica (MnFeOx-110) with high specific capacitance 224.6 F g−1 at 1 A g−1 was demonstrated.•MnO2//FeOOH replicas asymmetric supercapacitor showed high energy density of 51.5 Wh kg−1 and power density of 9.1 kW kg−1.
Controlled synthesis of tunable Mn-iron-oxide (Mn-FeOx) hybrids with unique three-dimensional (3D) porous structure based on diatoms for high performance supercapacitors is demonstrated. Successful transition process from MnO2 to FeOOH on diatomite was performed by two-step hydrothermal method and resultant replicas with 3D diatom morphology were obtained via etching process. The fabricated MnFeOx-0 diatom replica without transition was composed by MnO2 nanosheets and exhibited a high specific capacitance (228.6 F g−1 at 1 A g−1), good rate capability (74.6% retention after current density were increased to 10 A g−1), high coulombic efficiency (about 93.1% at 10 A g−1), and steady cycling performance (94.3% capacitance retention after 4000 cycles). MnFeOx-110 replica with FeOOH nanorods owned 224.6 F g−1 at 1 A g−1, high coulombic efficiency about 80% at 10 A g−1 and steady cycling performance about 92.5% retention after 4000 cycles. Finally, an asymmetric supercapacitor was assembled based on MnO2 nanosheets as the positive electrode and FeOOH nanorods as the negative electrode, which delivered a wide potential of 2 V with maximum energy density of 51.5 Wh kg−1 and power density of 9.1 kW kg−1. Considering that the two replicas owned great energy storage property, it opens an opportunity for rational design of the diatom morphology samples applied to high-performance supercapacitors.
A novel hierarchical nanotube array (NTA) with a massive layered top and discretely separated nanotubes in a core–shell structure, that is, nickel–cobalt metallic core and nickel–cobalt layered ...double hydroxide shell (NiCo@NiCo LDH), is grown on carbon fiber cloth (CFC) by template‐assisted electrodeposition for high‐performance supercapacitor application. The synthesized NiCo@NiCo LDH NTAs/CFC shows high capacitance of 2200 F g−1 at a current density of 5 A g−1, while 98.8% of its initial capacitance is retained after 5000 cycles. When the current density is increased from 1 to 20 A g−1, the capacitance loss is less than 20%, demonstrating excellent rate capability. A highly flexible all‐solid‐state battery‐type supercapacitor is successfully fabricated with NiCo LDH NTAs/CFC as the positive electrode and electrospun carbon fibers/CFC as the negative electrode, showing a maximum specific capacitance of 319 F g−1, a high energy density of 100 W h kg−1 at 1.5 kW kg−1, and good cycling stability (98.6% after 3000 cycles). These fascinating electrochemical properties are resulted from the novel structure of electrode materials and synergistic contributions from the two electrodes, showing great potential for energy storage applications.
Hierarchical nickel–cobalt@nickel–cobalt layered double hydroxide nanotube arrays with separated tubes and massive top are designed and fabricated by facile electrodeposition. The as‐prepared electrode possesses numerous electroactive sites, a highly conductive Ni/Co metallic core, and a high capacitance NiCo layered double hydroxide shell. The assembled battery‐type supercapacitor exhibits superior gravimetric capacitance, good rate performance, high specific energy, and high power density.
In this paper, a novel freestanding core‐branch negative and positive electrode material through integrating trim aligned Fe2O3 nanoneedle arrays (Fe2O3 NNAs) is first proposed with typical ...mesoporous structures and NiCo2O4/Ni(OH)2 hybrid nanosheet arrays (NiCo2O4/Ni(OH)2 HNAs) on SiC nanowire (SiC NW) skeletons with outstanding resistance to oxidation and corrosion, good conductivity, and large‐specific surface area. The original built SiC NWs@Fe2O3 NNAs is validated to be a highly capacitive negative electrode (721 F g−1 at 2 A g−1, i.e., 1 F cm−2 at 2.8 mA cm−2), matching well with the similarly constructed SiC NWs@NiCo2O4/Ni(OH)2 HNAs positive electrode (2580 F g−1 at 4 A g−1, i.e., 3.12 F cm−2 at 4.8 mA cm−2). Contributed by the uniquely engineered electrodes, a high‐performance asymmetric supercapacitor (ASC) is developed, which can exhibit a maximum energy density of 103 W h kg−1 at a power density of 3.5 kW kg−1, even when charging the device within 6.5 s, the energy density can still maintain as high as 45 W h kg−1 at 26.1 kW kg−1, and the ASC manifests long cycling lifespan with 86.6% capacitance retention even after 5000 cycles. This pioneering work not only offers an attractive strategy for rational construction of high‐performance SiC NW‐based nanostructured electrodes materials, but also provides a fresh route for manufacturing next‐generation high‐energy storage and conversion systems.
An asymmetric supercapacitor device based on the advanced Fe2O3 nanoneedle arrays with typical mesoporous structures and NiCo2O4/Ni(OH)2 hybrid nanosheet arrays‐decorated SiC nanowire supporters with versatile advantages on carbon cloth as negative and positive electrodes is designed successfully, and the assembled device can exhibit large‐specific capacitance, high‐energy density, and excellent cycling stability.
Hierarchical NiMoO4 architectures assembled from well‐aligned uniform nanosheets or nanorods are successfully grown on various conductive substrates using a facile and effective general approach. ...Importantly, the nanostructures of NiMoO4 can be easily controlled to be nanosheets or nanorods by using different solvents. By virtue of their intriguing structure features, NiMoO4 nanosheets as integrated additive‐free electrodes for supercapacitors manifest higher Faradaic capacitance than NiMoO4 nanorods. Moreover, an asymmetric supercapacitor (ASC) is constructed using the as‐prepared NiMoO4 nanosheets as the positive electrode and activated carbon (AC) as the negative electrode. The optimized ASC with an extended operating voltage range of 0–1.7 V displays excellent electrochemical performance with a high energy density of 60.9 Wh kg−1 at a power density of 850 W kg−1 in addition to superior rate capability. Furthermore, the NiMoO4//AC ASC device exhibits remarkable cycling stability with 85.7% specific capacitance retention after 10 000 cycles. The results show that these NiMoO4‐based nanostructures are promising for high‐energy supercapacitors.
Hierarchical NiMoO4 nanosheet and nanorod arrays are successfully grown on various conductive substrates using a facile and effective solution method. Combined with activated carbon, the integrated NiMoO4‐Ni foam electrode is successfully used to construct a high‐performance asymmetric supercapacitor that has high energy density and remarkable cycling stability.
Despite possessing 3D network structure, the electrochemical behaviors of binder-free electrodes using carbonized melamine foam (CMF) as scaffold are still limited in supercapacitors (SCs), which is ...mainly due to the CMF scaffold with some damaged carbonized skeleton after high temperature carbonization. Herein, an efficient binder-free electrode (NiCo2O4/MCMF) with multiple carbonized channels wrapped by NiCo2O4 nanosheets has been successfully fabricated, which is realized by using carbon nanofibers-modified CMF (MCMF) as scaffold through chemical vapor deposition (CVD). Remarkably, numerous branched carbon nanofibers interconnect with each other around the carbonized skeleton in MCMF, not only providing multiple conductive channels for rapid charge transport and ionic diffusion, but also allowing the high mass-loading of pseudocapacitive NiCo2O4 nanosheets. The resultant NiCo2O4/MCMF binder-free electrode delivers a high specific capacitance (1541 F g−1 at 1 A g−1) with excellent durability (85.8% capacitance retention after 10000 cycles at 10 A g−1). Furthermore, a kind of high performance asymmetric SCs (ASC) are assembled using NiCo2O4/MCMF as positive electrode and MCMF as negative electrode. The ASCs exhibit low internal resistance, maximum energy density (53.1 Wh kg−1) and power density (18000 W kg−1), which can act as efficient energy storage devices to supply power without obvious degradation after repeating.
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•An efficient binder-free electrode has been put forward.•Multiple carbonized channels are wrapped by NiCo2O4 nanosheets.•The electrode delivers a large specific capacitance with strong durability.•Asymmetric supercapacitors with high energy/power density are fabricated.
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•Hierarchically hollow Co3O4/polyaniline nanocages (Co3O4/PANI NCs) were designed and synthesized.•Co3O4/PANI NCs have hollow structure, high surface area, and high ...conductivity.•Co3O4/PANI NCs electrode has high specific capacitance, and good cycle stability.
Hierarchically hollow Co3O4/polyaniline nanocages (Co3O4/PANI NCs) with enhanced specific capacitance and cycle performance for electrode material of supercapacitors are fabricated by combining self-sacrificing template and in situ polymerization route. Benefiting from the good conductivity of PANI improving an electron transport rate as well as high specific surface area from such a hollow structure, the electrode made of Co3O4/PANI NCs exhibits a large specific capacitance of 1301 F/g at the current density of 1 A/g, a much enhancement is obtained as compared with the pristine Co3O4 NCs electrode. The contact resistance (Re), charge-transfer (Rct) and Warburg resistance of Co3O4/PANI NCs electrode is significantly lower than that of the pristine Co3O4 NCs electrode, indicating the enhanced electrical conductivity. In addition, the Co3O4/PANI NCs electrode also displays superior cycling stability with 90 % capacitance retention after 2000 cycles. Moreover, an aqueous asymmetric supercapacitor was successfully assembled using Co3O4/PANI NCs as the positive electrode and activated carbon (AC) as the negative electrode, the assembled device exhibits a superior energy density of 41.5 Wh/kg at 0.8 kW/kg, outstanding power density of 15.9 kW/kg at 18.4 Wh/kg, which significantly transcending those of most previously reported. These results demonstrate that the hierarchically hollow Co3O4/PANI NCs composites have a potential for fabricating electrode of supercapacitors.
A flexible all-solid-state asymmetric supercapacitor was successfully assembled using petal-like NiCo2S4/Polyaniline (PANI) nanosheets as the positive electrode, which exhibited an excellent ...electrochemical performance owing to the integration of Polyaniline into NiCo2S4 nanosheets.
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•Petal-like NiCo2S4/Polyaniline (PANI) nanosheets electrode was fabricated.•The integration of PANI enhances ion-accessibility and efficient charge transportation.•The open space between interconnected nanosheets serve as “ion-buffering reservoirs”.•A flexible all-solid-state asymmetric supercapacitor achieves high energy density and power density.
The synthesis of NiCo2S4 as electroactive material has been well reported, however, fabricating a NiCo2S4 electrode with excellent electrochemical performance at high current density remains a challenge. Herein, we developed a supercapacitor electrode comprising petal-like NiCo2S4/Polyaniline (PANI) nanosheets via a simple hydrothermal route coupled with a chemical oxidative polymerization. Benefiting from the integration of PANI, which greatly enhance ion-accessibility and lead to more efficient charge transportation, the resultant NiCo2S4/PANI electrode exhibited a high specific capacitance of 1879Fg−1 at a current density of 1Ag−1 and an excellent rate capability of 72% at 20Ag−1, after 2000 cycles, only 8.9% loss of initial capacitance at a high charge/discharge current density of 8Ag−1. Moreover, a flexible all-solid-state asymmetric supercapacitor was successfully assembled using NiCo2S4/PANI as the positive electrode and activated carbon (AC) as the negative electrode, the assembled device exhibits a superior energy density of 54.06Whkg−1 at 0.79kWkg−1, outstanding power density of 27.1kWkg−1 at 15.9Whkg−1, which significantly transcending those of most previously reported. This study shows that the prepared NiCo2S4/PANI electrode offers great potential in energy storage device applications.
A significant advance toward the design and fabrication of a novel hierarchical supercapacitor electrode consisting of FeCo2S4‐tubes with well‐defined square cross‐section and intersecting nanosheets ...built porous shells on a 3D porous Ni backbone via controlled sulfidation is reported. This general method allows template‐free synthesis of metal sulfides tubular structures with polygonal cross‐sections and also fine control over the nanostructure leading to both maximized porosity and saturation sulfidation. New insights into concentration and time dependent sulfidation reaction kinetics are proposed. The FeCo2S4 electrode achieves a specific capacitance reaching 2411 F g‐1 at 5 mA cm‐2 and good rate capability, which are superior over those for nanotube arrays of other ternary transition metal sulfides. This is attributed to rich redox reactions, the highly porous but robust architecture as well as high electrical conductivity. Especially such porous shells effectively avoid “dead volume”, thus improve the utilization ratio of the electrode material. Asymmetric solid‐state device applying the FeCo2S4 as positive electrode and N‐doped graphene hydrogel film as negative electrode has a high cell voltage of 1.6 V and thus delivers considerably higher energy density of 76.1 W h kg‐1 (at 755 W kg‐1) than those reported for similar devices.
General controlled sulfidation results in a novel hierarchical supercapacitor electrode consisting of FeCo2S4‐tubes with well‐defined square cross‐section and intersecting nanosheets built porous shells on a 3D porous Ni backbone, which shows high specific capacitances, good rate‐capability and excellent cycling‐stability due to the highly porous but robust architecture, rich redox reactions as well as high conductivity.
The synthesis of layered double hydroxide (LDH) as electroactive material has been well reported; however, fabricating an LDH electrode with excellent electrochemical performance at high current ...density remains a challenge. In this paper, we report a 3D hierarchical porous flower-like NiAl-LDH grown on nickel foam (NF) through a liquid-phase deposition method as a high-performance binder-free electrode for energy storage. With large ion-accessible surface area as well as efficient electron and ion transport pathways, the prepared LDH-NF electrode achieves high specific capacity (1250 C g−1 at 2 A g−1 and 401 C g−1 at 50 A g−1) after 5000 cycles of activation at 20 A g−1 and high cycling stability (76.7% retention after another 5000 cycles at 50 A g−1), which is higher than those of most previously reported NiAl-LDH-based materials. Moreover, a hybrid supercapacitor with LDH-NF as the positive electrode and porous graphene nanosheet coated on NF (GNS-NF) as the negative electrode, delivers high energy density (30.2 Wh kg−1 at a power density of 800 W kg−1) and long cycle life, which outperforms the other devices reported in the literature. This study shows that the prepared LDH-NF electrode offers great potential in energy storage device applications.
A hybrid supercapacitor (LDH-NF//GNS-NF) delivers a high energy density (30.2 Wh kg−1 at a power density of 800 W kg−1) and long cycle life (15,000 cycles) with a specific capacity of 56 C g−1 (70% retention at 10 A g−1). Display omitted
•Layered double hydroxide is grown on nickel foam by liquid phase deposition method.•The electrode shows excellent performance at high current density (50 A g−1).•The assembled hybrid supercapacitor exhibits good electrochemical performance.
The electrochemical performance of nanostructured nickel-cobalt sulfides is greatly limited by the sluggish reaction kinetics and limited electroactive sites. Herein, we design and synthesize ...free-standing Se doped nickel-cobalt sulfides with controllable-component directly on carbon cloth, which involves the hydrothermal process and sulfuration/selenylation reaction. Serving as free-standing electrode, as-synthesized Se doped nickel-cobalt sulfides not only favor the fast ion diffusion path and low contact resistance, but also provide rich electroactive sites with electrolyte. More importantly, proper Se doping in nickel-cobalt sulfides greatly increases the electrochemically active surface area and reduces the charge transfer resistance. Based on the X-ray photoelectron spectroscopy and transmission electron microscopy results, the reaction mechanism is convincingly revealed that Se dopants have been changed into SeOx. And electrochemical activated oxyhydroxides are mainly involved in electrochemical reactions. As a result, as-fabricated Se doped nickel-cobalt sulfides show a good electrochemical performance for supercapattery. Further, the supercapattery device is also assembled by using nickel-cobalt sulfide/selenide as positive electrode and activated carbon as negative electrode, which shows a high energy density of 39.6 Wh kg−1 at the power density of 1501 W kg−1.
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•Se doping can provide large the active sites and fast electron transport path.•The Se doped nickel-cobalt sulfides show good electrochemical performances.•The NiCo2S2.2Se1.8//AC device shows a high energy density of 39.6 Wh kg−1.
