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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.
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.
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.
A metal oxide modified interface method was developed to boost the supercapacitor properties in both three-electrode system and ASC device.
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•PEDOT-Ni2+/NiO-substrate electrode was ...fabricated via stepwise electrodeposition.•This electrode obtained high specific capacitance and superior cycling stability.•Ni2+/NiO-PEDOT//PEDOT ASC cell presented higher energy density and power density.•This structure could facilitate the transfer of electrolyte ions.•This structure achieved long cyclic lifetime and high electrochemical stability.
Poly(3,4-ethylene-dioxythiophene) (PEDOT) was reported to be an organic electrode material for supercapacitor. But poor stability and small capacitance restrict its further application. Here, we fabricate a new PEDOT-based supercapacitor device where the working electrode is prepared by depositing trace of Ni-rich oxide on the interface between PEDOT and substrate (named as PEDOT-Ni2+/NiO-SS). This PEDOT-Ni2+/NiO-SS half-electrode obtained a higher specific capacitance of 236 F/g, good rate capability and superior cycling stability (99% capacitance retention after 2500 cycles) than those of untreated PEDOT. Subsequently, a flexible all-solid-state asymmetric supercapacitor (ASC) device was fabricated by using PEDOT-Ni2+/NiO-carbon cloth as positive electrode and untreated PEDOT-carbon cloth as negative electrode. An ASC cell presented higher energy density (40.15 Ah/Kg) and power density (1.32 kW/Kg) than the symmetrical supercapacitor device composed of untreated PEDOT. PEDOT-Ni2+/NiO-SS structure could facilitate the insertion of ions from electrolytes into electrode material, achieve long cyclic lifetime and high electrochemical stability. The electrochemical deposition method to modify electrode interface using metal oxide could be a promising strategy and pave the way for the preparation of other supercapacitor electrodes.
Three-dimensional hierarchical NiCo2O4/Ni2P electrodes have been successfully synthesized for advanced asymmetric supercapacitors.
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•Hierarchical NiCo2O4/Ni2P electrodes on nickel foam ...are rationally constructed.•This unique structure provides more electroactive sites for Faradaic reaction.•The NiCo2O4/Ni2P-30 electrode exhibits a high specific capacity of 2900 F g−1.•The assembled asymmetric supercapacitor can easily power 14 LEDs.
Herein, a novel three-dimensional hierarchical NiCo2O4/Ni2P structure is successfully fabricated through a facile hydrothermal and subsequent electrodeposition process. One-dimensional Ni2P nanoneedles decorate on two-dimensional NiCo2O4 nanosheets can effectively enhance the electrical conductivity and surface area of NiCo2O4 to promote fast Faradaic reaction. The optimized NiCo2O4/Ni2P-30 electrode exhibits a high specific capacity of 2900 F g−1 at 0.008 A cm−2. Moreover, an asymmetric supercapacitor (ASC) is fabricated by using the NiCo2O4/Ni2P-30 as positive electrode and activated carbon as the negative electrode, the device achieves an excellent electrochemical property with the energy density of 40.7 W h kg−1 at 800 W kg−1. Besides, the as-assembled device also exhibits an excellent cycling performance of ∼92.0% of initial capacitance after 5000 cycles indicating its outstanding conductivity and structural stability. All of the results demonstrate that the hierarchical NiCo2O4/ Ni2P composites are electrodes in energy storage application.
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•Phytic acid is used to synthesize stable nanohybrids of NiCo2S4 with RGO.•The morphology of NiCo precursor could be tuned from nanosheets to nanoparticles.•The hybrid supercapacitor ...exhibits prominent electrochemical performance.•The NiCo2S4/PRGO nanohybrids expose enhanced active surface area.
Incorporating graphene with transition metal sulfides nanoparticles (NPs) holds great potential as a high performance battery-type electrode for hybrid supercapacitors (HSCs). However, the poor interfacial contact between NPs and graphene sheets usually leads to compromised capacitance and stability of electrode materials. In order to tackle this problem, eco-friendly phytic acid (PA) is used as a bridging connection between graphene and NiCo2S4 NPs via the six phosphate groups of PA to afford NiCo2S4 NPs immobilized firmly on phytic acid modified reduced graphene oxide (PRGO) sheets. In addition, the morphology of NiCo precursor could be easily tuned by the addition of PA. Benefiting from the morphology and composition, the prepared NiCo2S4/PRGO hybrid battery-type electrode exhibits excellent electrochemical performance with high capacitance (1090 F g−1 at 2 A g−1), good rate performance (76.1% of the capacitance can be retained from 2 to 20 A g−1) and enhanced cycling stability. Moreover, a HSC device is fabricated using NiCo2S4/PRGO hybrid as positive electrode and active carbon (AC) as negative electrode, which exhibits a prominent energy density of 27.5 Wh kg−1 at a high power density of 446.5 W kg−1. The utilization of PA could offer a new avenue for the design of transition metal sulfides/PRGO hybrid for electrochemical or electrocatalytic applications.
