As-assembled Device Research Articles

Regulating the core/shell electric structure of Co3O4@Ni–Co layered double hydroxide on Ni foam through electrodeposition for a quasi-solid-state supercapacitor

A flower-like structured electrode material of Co3O4@Ni–Co layered double hydroxide (LDH) grown on Ni foam (Co3O4@Ni–Co LDH/NF) was prepared via an in situ growth, annealing and electrodeposition process. The Co3O4@Ni–Co LDH/NF electrode was prepared with the optimized conditions of annealing temperature 300 °C, deposition time 20 min and Ni/Co ratio 1:1. The results showed that the as-prepared electrode material exhibited an excellent specific capacitance and great cycling stability. Furthermore, an quasi-solid-state supercapacitor was assembled using the prepared Co3O4@Ni–Co LDH/NF as the positive electrode and activated carbon on Ni foam (AC/NF) as the negative electrode. The as-assembled device presented a high energy density and power density.

Effect of Reaction Time on the Performance of Co3O4 Electrode Materials for High Performance Supercapacitors

Electrochemical performance of the material depends on the morphology and structural characteristics of the material. Co3O4 samples shows the remarkable electrochemical performance owing to the high porosity, appropriate pore size distribution and novel architecture and reaction time effect of morphology. In this work, Co3O4 nanowires grown on Ni foam have been synthesized through a facile hydrothermal approach, revealing large capacitance of 2178.4 mF cm-2 at the current density of 2 mA cm-2 and cycling stability with 79.6% capacitance retention after 6000 cycles. The as-assembled device delivers excellent electrochemical performance for high specific capacitance of 356 mF cm-2 at the current density of 2 mA cm-2 and high cycle stability.

Core–shell crystalline ZIF-67@amorphous ZIF for high-performance supercapacitors

Zeolitic imidazolate frameworks (ZIFs)-based core–shell structured nanomaterials were synthesized. As supercapacitor electrode materials, they exhibit excellent performance due to the advanced intrinsic properties of ZIFs, such as high porosity, good stability and large surface area. The materials were characterized by SEM, TEM, XRD, FT-IR, XPS and BET. When synthesized core–shell structured nanomaterial was tested in a 3-electrode system, it exhibited a high specific capacitance of 1176.8 F g−1 at a current density of 1 A g−1 and a good cycling performance with 98.3% initial capacity retention after 1000 continuous charge–discharge cycles. An asymmetric supercapacitor (ASC) device was assembled by employing ZIF-67@amorphous ZIF and activated carbon as positive and negative electrode materials, respectively. The as-assembled ASC devices exhibited excellent stability that retained almost 100% of the initial capacity after 2000 cycles. To demonstrate the practical application of the ASC, two simple fully charged ASCs can light up the LED for over 2 min, which proved that the core–shell structured ZIF-67@amorphous ZIF material has a suitable potential for supercapacitor applications.

Highly Sensitive Narrowband Si Photodetector With Peak Response at Around 1060 nm

Photodetection at a wavelength of about 1060 nm is very important for applications including medical imaging, optical communication, and light detection and ranging. In this article, a self-powered near-infrared light detector with a narrowband at around 1060 nm is realized based on a simple Si Schottky structure, in which the Ohmic and Schottky electrodes are configured on the front and rear surfaces of the Si substrate, respectively. The as-assembled device exhibits a tunable peak response near 1060 nm with a full width at half maximum of 107 nm, which could be due to the combined effect of the narrow photo-current generation and the self-filtering effect of the silicon substrate. At zero bias, a specific detectivity of ~1 x 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> Jones and linear dynamic range about 101 dB are achieved, in spite of the weak absorption of Si at this wavelength. The external quantum efficiency can be improved to 135% under a low bias of -1 V, indicating the existence of gain mechanism during photodetection. Finally, it is also found that the asassembled near-infrared device shows excellent antiinterference capability during the photodetection process.These results corroborate that the present Si photodetector may find promising application in future near-infrared optoelectronic devices and systems.

Electrospun Nb2O5 nanorods/microporous multichannel carbon nanofiber film anode for Na+ ion capacitors with good performance

For the disadvantages of both the slow reaction kinetics and the poor conductivity for Nb2O5 electrode materials as sodium-ion capacitors (SICs), Nb2O5 NRs/NMMCNF film electrode with good flexibility and high electrochemical property has been fabricated by electrospinning PAN/PMMA/H2Nb2O6·H2O homogeneous viscous suspension and followed by an annealing treatment, in which the precursor H2Nb2O6·H2O nanorods are obtained by grinding H2Nb2O6·H2O nanowires, and Nb2O5 nanorods are uniformly embedded in nitrogen doped microporous multichannel carbon nanofiber. Benefiting from the multichannel network structure, Nb2O5 NRs/NMMCNF film electrode delivers the fast kinetics of Na+-storage and the superior Na-ion storage performance, it delivers outstanding rate capability (101 mAh g−1 at 4 A g−1) and ultralong lifespan (91% capacity retention after 10,000 cycles at 2 A g−1). A Nb2O5 NRs/NMMCNF//AC SIC based on the Nb2O5 NRs@NMMCNF fiber film anode and the AC cathode is assembled. The energy density of the as-assembled device is as high as 91 Wh kg−1 and its maximum power density is 7499 W kg−1. This work offers a new structure design strategy toward intercalation-type metal oxide electrodes for application in SICs.

Preaddition of Cations to Electrolytes for Aqueous 2.2 V High Voltage Hybrid Supercapacitor with Superlong Cycling Life and Its Energy Storage Mechanism.

Electrolyte solutions and electrode active materials, as core components of energy storage devices, have a great impact on the overall performance. Currently, supercapacitors suffer from the drawbacks of low energy density and poor cyclic stability in typical alkaline aqueous electrolytes. Herein, the ultrathin Co3O4 anode material is synthesized by a facile electrodeposition, followed by postheat treatment process. It is found that the decomposition of active materials induces reduction of energy density and specific capacitance during electrochemical testing. Therefore, a new strategy of preadding Co2+ cations to achieve the dissolution equilibrium of cobalt in active materials is proposed, which can improve the cyclic lifetime of electrode materials and broaden the operation window of electrochemical devices. Co2+ and Li+ embedded in carbon electrode during charging can enhance H+ desorption energy barrier, further hampering the critical step of bulk water electrolysis. More importantly, the highly reversible chemical conversion mechanism between Co3O4 and protons is demonstrated to be the fact that a large amount of quantum dots and second-order flaky CoO layers were in situ formed in the electrochemical reaction process, which is first discovered and reported in neutral solutions. The as-assembled device achieves a high operation voltage (2.2 V), excellent cycling stability (capacitance retention of 168% after 10 000 cycles) and ultrahigh energy density (99 W h kg-1 at a power density of 1100 W kg-1). The as-prepared electrolytes and highly active electrode materials will open up new opportunities for aqueous supercapacitors with high safety, high voltage, high energy density, and long-lifespan.

Cu(I)/Cu(II) partially substituting the Co(II) of spinel Co3O4 nanowires with 3D interconnected architecture on carbon cloth for high-performance flexible solid-state supercapacitors

The 3D interconnected architecture nanowires of Co3O4 partially substituted by Cu(I)/Cu(II) coated on the carbon cloth ([email protected]) with high specific surface area were fabricated by a facile and low-cost hydrothermal approach and consequent thermal annealing. The prepared binder-free [email protected] electrode exhibits high specific capacitance (1947.2 F g−1 or 973.6 C g−1 at 1 A g−1) and superior cyclic stability (93.76% retention of initial value up to 10,000 cycles). In addition, the [email protected] and synthesized Fe2O3@CC are used as positive and negative electrodes in the presence of PVA-KOH as a gel electrolyte to assemble a flexible solid-state asymmetric supercapacitor. The as-assembled flexible device shows a high specific capacitance of 182.7 F g−1, high energy density of 57.1 W h kg−1 at the power density of 749.75 W kg−1, remarkable cyclic stability with 93.25% retention after 10,000 cycles and almost no capacity loss under different bending angles. Therefore, this material has potential application for wearable electronics with the excellent mechanical flexibility.

Facile synthesis of freestanding cellulose/RGO/silver/Fe2O3 hybrid film for ultrahigh-areal-energy-density flexible solid-state supercapacitor

We report the design of a freestanding cellulose/RGO/silver/Fe2O3 hybrid film for direct use as electrodes for construction of high-performance flexible solid-state supercapacitor (FSS). It is well characterized and found to feature noticeable capacitive properties due to the unique structure, high conductivity and dual electroactive species (i.e., RGO and Fe2O3) for charge storage. As demonstrated in a three-electrode system, such film electrode achieves the maximum areal and volumetric capacitance of 2044 mF cm−2 and 75.7 F cm−3, respectively, with prominent rate performance and long-term cyclic durability. Later, a symmetric FSS device is constructed by employing this film as both anode and cathode electrodes. The as-assembled device offers the highest areal and volumetric capacitance of 1132 mF cm−2 and 18.2 F cm−3, respectively, displays inconspicuous performance degradation under different curved states, and possesses the largest areal energy density of 226.4 μWh cm−2, which is far better than that of many advanced symmetric and asymmetric flexible supercapacitors. The attractive capacitive behaviors and easy fabrication processes could render cellulose/RGO/silver/Fe2O3 hybrid film a promising material for the applications in next-generation flexible and wearable electronics in the future.

Hierarchical design of Cu-Ni(OH)2/Cu-MnxOy core/shell nanosheet arrays for ultra-high performance of asymmetric supercapacitor

Supercapacitors lack high energy density and long term stability, so a new class of hybrid material with hierarchical structure is desirable. Herein, for the first time we are reporting a rational design of hierarchical Cu-Ni(OH)2/Cu-MnxOy core/shell nanosheet arrays. The Cu-Ni(OH)2/Cu-MnxOy nanosheet arrays were synthesized by a two-step hydrothermal reaction. The as-synthesized Cu-Ni(OH)2/Cu-MnxOy hybrid structure exhibits ultrahigh areal and specific capacitances of 10.14 F cm−2 and 2535 F g−1, respectively at 3 mA cm−2. The electrode exhibits high rate-capability (59.37%) and excellent capacitance retention of 93.09% after 10 000 cycles. In Cu-Ni(OH)2/Cu-MnxOy core/shell hybrid structure, highly conductive and electroactive Cu-Ni(OH)2 core and Cu-MnxOy shell components played a vital role to develop a high-performance and stable electrode material. Furthermore, the unique porous structure of Cu-Ni(OH)2/Cu-MnxOy also provides enough space and short-diffusion lengths for Faradaic reaction. The asymmetric supercapacitors assembled of Cu-Ni(OH)2/Cu-MnxOy as positive electrode and GR/CNTs as negative electrode delivers a high specific capacitance of 267.15 F g−1 at a current density of 1 A g−1 with high-rate capability of 60.30%. Moreover, the as-assembled ASC device also shows an ultra-high energy density of 94.98 W h kg−1 at a power density of 759.89 W kg−1 and a maximum power density of 15 173.5 W kg−1 at an energy density of 57.28 W h kg−1 with capacitance retention of 89.79% after 10 000 cycles. These outstanding results suggest that Cu-Ni(OH)2/Cu-MnxOy hybrid structure can be considered as a cathode material for asymmetric supercapacitor in future.

Flexible quasi-solid-state dual-ion asymmetric supercapacitor based on Ni(OH)2 and Nb2O5 nanosheet arrays

Increasing the energy density, power density as well as widening the operation voltage are essential to electrochemical capacitors to meet the practical energy demands. Herein, a novel flexible quasi-solid-state dual-ion asymmetric supercapacitor (ASC) with Ni(OH)2 and Nb2O5 nanosheets directly grown on stainless steel mesh is developed. In the dual-ion ASC, Nb2O5 negative and Ni(OH)2 positive electrodes react with Li+ and OH− respectively in alkaline gel electrolyte to store energy, which is quite different from conventional alkali metal ion SCs and alkaline SCs. The as-assembled flexible device has an extended working voltage of 1.7 V and delivers a capacity of 5.37 mAh cm−2, a maximum energy density and power density of 0.52 mWh cm−3 and 170 mW cm−3, respectively. The device maintains around 60% capacity retention after long cycling up to 1000 cycles. Moreover, our device can light up a LED light efficiently upon fast charging. The proposed quasi-solid-state dual-ion ASC has potential applications in future portable electronics and flexible energy storage devices.

Transition metal oxide@hydroxide assemblies as electrode materials for asymmetric hybrid capacitors with excellent cycling stabilities.

In this work, three-dimensional cactus-like Co3O4@Ni(OH)2 electrode materials are grown directly on Ni foam via a two-step hydrothermal method. The as-prepared products possess a specific capacitance of 464.5 C g−1 at 0.5 A g−1 and 91.67% capacitance retention after 20 000 cycles. The as-assembled device using the as-synthesized samples as positive electrodes delivers an energy density of 112.5 W h kg−1 at a power density of 1350 W h kg−1. The superior electrochemical performance of the electrode materials can be attributed to their unique structure, the synergistic effect between Co3O4 and Ni(OH)2 materials and reversible reaction kinetics. It suggests that the products are potential alternatives in future energy storage devices.

Biomass waste-derived nitrogen-rich hierarchical porous carbon offering superior capacitive behavior in an environmentally friendly aqueous MgSO4 electrolyte

Nitrogen-doped porous carbons have been extensively investigated to improve the specific capacitance in aqueous electrolytes by increasing the specific surface area and nitrogen content and by optimizing the pore structure. However, research on the effect of electrolyte cations on the specific capacitance of these materials is rare, especially for neutral electrolytes. Herein, a nitrogen-rich hierarchically porous carbon (NRHPC) with a high nitrogen content of 12.3 atm% is successfully prepared by pyrolyzing a mixture of bagasse, K2CO3 and urea in a mass ratio of 2:1:4. It is found that NRHPC shows superior electrochemical performance in MgSO4 than in Li2SO4 electrolyte, with specific capacitances of 315.0, 274.4, and 188.1 F g−1 at 1.0, 10.0, and 100 A g−1, respectively. Furthermore, it is found that the capacitance enhancement is closely related to the nitrogen content of the porous carbon materials. Theoretical calculation reveals that the Mg2+ ions have higher affinity towards the N atoms than Li+, producing higher charge storage capability via interaction between the Mg2+ and N atoms. When the 1.0 M MgSO4 is used as electrolyte, a symmetric capacitor based on the nitrogen-rich hierarchically porous carbon shows a high energy density of 39.5 Wh kg−1 at a power density of 0.9 kW kg−1. Moreover, this as-assembled device displays superior long-term cycling stability, with a capacitance retention of >96.2% after 10,000 cycles at 10.0 A g−1.

Dual-plasmonic Au/graphene/Au-enhanced ultrafast, broadband, self-driven silicon Schottky photodetector

High-performance photodetectors are desirable for various applications, including multi-wavelength image sensing, communication, and safety monitoring. In this study, we report the construction of a dual-surface plasmon-enhanced silicon Schottky photodetector using Au nanoparticles (NPs)/graphene/Au NPs hybrid structure as the electrode. It was found that the as-assembled device exhibited broad sensitivity, ranging from ultraviolet to near-infrared light (360–1330 nm) at room temperature, with a high response speed of 360 ns and a 3 dB bandwidth of 780 kHz at zero bias. Further theoretical simulation based on the finite-element method revealed that good device performance is associated with the contribution of the Au NPs/graphene/Au NPs electrode: intense dual-plasmonic resonance coupling is induced in a hybrid structure of two layers of metallic NPs separated by a uniform monolayer graphene. It not only can enhance light trapping and the localized electric field at the resonant and off-resonant wavelength regions, but is also beneficial for the tunneling of hot electrons. This work demonstrated the great potential of dual-plasmonic resonance coupling in optoelectronic devices and will lead to the development of advanced plasmonic devices.

All-Solid-State Fiber-Shaped Asymmetric Supercapacitors with Ultrahigh Energy Density Based on Porous Vanadium Nitride Nanowires and Ultrathin Ni(OH)2 Nanosheet Wrapped NiCo2O4 Nanowires Arrays Electrode

Fiber-shaped supercapacitors (FSC), among the most promising next-generation flexible energy storage devices, attract tremendous attention due to their high power density and rapid charging and discharging. However, their practical application is hindered by the low energy density that results from inferior specific capacitance and a limited voltage window. Herein, we design a flexible fiber-shaped asymmetric supercapacitor (FASC) with high energy density using vanadium nitride (VN) nanowires (NWs) on carbon nanotube fiber (CNTF) as negative electrode and ultrathin Ni(OH)2 nanosheet wrapped nickel cobalt oxide (NiCo2O4) to form a hierarchical nanowire array (HNWA) structure on CNTF as positive electrode. As-assembled FASC device has a maximum operational voltage of 1.6 V, with a highest areal capacitance of 291.9 mF/cm2 (106.1 F/cm3) and an energy density of 103.8 μWh/cm2 (37.7 mW/cm3). The FASC device possesses excellent reliability and achieves a retaining capacitance of more than 90% after 3000 bending...

Facile synthesis of NiO nanocubes for photocatalysts and supercapacitor electrodes

Herein, NiO nanocubes are prepared through a simple hydrothermal route. The as-synthesized product shows excellent photocatalytic properties for dye degradation, revealing that the photocatalytic degradation efficiency for Congo red is higher than other commonly used dyes. In addition, due to its unique structure, the resulting product as the electrode material shows excellent electrochemical performance. The specific capacitance of 1012 mF cm−2 can be achieved at a current density of 1 mA cm−2. Simultaneously, the as-assembled device shows good cycle performance with the capacitor retention rate of 89.3% after 10000 cycles. It indicates the as-prepared product can be used as an efficient photocatalyst and energy storage device.

A novel three-dimensional hierarchical NiCo2O4/Ni2P electrode for high energy asymmetric supercapacitor

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.

Self-template synthesis of double shelled ZnS-NiS1.97 hollow spheres for electrochemical energy storage

In this work, double shelled ZnS-NiS1.97 hollow spheres have been achieved via a simple self-template route, which involves the synthesis of Zn-Ni solid spheres precursors as the self-template and then transformation into double shelled ZnS-NiS1.97 hollow spheres by sulfidation treatment. The as-prepared double shelled ZnS-NiS1.97 hollow spheres possess a high surface area (105.26 m2 g−1) and porous structures. Benefiting from the combined characteristics of novel structures, multi-component, high surface area and porous. When applied as electrode materials for supercapacitors, the double shelled ZnS-NiS1.97hollow spheres deliver a large specific capacitance of 696.8C g−1 at 5.0 A g−1 and a remarkable long lifespan cycling stability (less 5.5% loss after 6000 cycles). Moreover, an asymmetric supercapacitor (ASC) was assembled by utilizing ZnS-NiS1.97 (positive electrode) and activated carbon (negative electrode) as electrode materials. The as-assembled device possesses an energy density of 36 W h kg−1, which can be yet retained 25.6 W h kg−1 even at a power density of 2173.8 W Kg−1, indicating its promising applications in electrochemical energy storage. More importantly, the self-template route is a simple and versatile strategy for the preparation of metal sulfides electrode materials with desired structures, chemical compositions and electrochemical performances.

Hierarchical CuCo2O4@nickel-cobalt hydroxides core/shell nanoarchitectures for high-performance hybrid supercapacitors

Ni0.5Co0.5(OH)2 nanosheets coated CuCo2O4 nanoneedles arrays were successfully designed and synthesized on carbon fabric. The core/shell nanoarchitectures directly served as the binder-free electrode with a superior capacity of 295.6mAhg−1 at 1Ag−1, which still maintained 220mAhg−1 even at the high current density of 40Ag−1, manifesting their enormous potential in hybrid supercapacitor devices. The as-assembled CuCo2O4@Ni0.5Co0.5(OH)2//AC hybrid supercapacitor device exhibited favorable properties with the specific capacitance as high as 90Fg−1 at 1Ag−1 and the high energy density of 32Whkg−1 at the power density of 800Wkg−1. Furthermore, the as-assembled device also delivered excellent cycling performance (retaining 91.9% of the initial capacitance after 12,000 cycles at 8Ag−1) and robust mechanical stability and flexibility, implying the huge potential of present hierarchical electrodes in energy storage devices.

Hierarchical Core-Shell Nanosheet Arrays with MnO2 Grown on Mesoporous CoFe2O4 Support for High-Performance Asymmetric Supercapacitors

We demonstrated the design and fabrication of unique core-shell CoFe2O4@MnO2 nanosheets arrays (NSAs) on nickel foam via a facile and scalable method. The CoFe2O4 nanosheets (NSs) grown on the nickel foam acted as a porous skeleton with large surface areas for the growth of MnO2 NSs, achieving the enhancement of both the electrical and the ionic conductivities. Ultrathin MnO2 NSs were found vertically grown on the CoFe2O4 NSs in a core-shell nanoarchitecture. Its thickness can be controlled by retention times during the hydrothermal process. The obtained CoFe2O4@MnO2 NSAs electrode achieved a highly enhanced areal capacitance of 3.59Fcm−2 at a current density of 2mAcm−2. An aqueous asymmetric supercapacitor (ASC) device was assembled using CoFe2O4@MnO2 NSAs as its positive electrode and the activated carbon (AC) as its negative electrode. The as-assembled ASC device can be operated in a voltage region of 1.6V and exhibited a specific capacitance of 103.86Fg−1 at 5mAcm−2. Its energy density and power density were as high as 37W h kg−1 at 470Wkg−1 and 4800Wkg−1 at 15.3W h kg−1, respectively. These remarkable electrochemical properties suggested that such CoFe2O4@MnO2 NSAs nanoarchitecture could be one of a potential candidates for the next generation energy storage devices with higher energy density delivery.

One-pot synthesis of heterogeneous Co3O4-nanocube/Co(OH)2-nanosheet hybrids for high-performance flexible asymmetric all-solid-state supercapacitors

Abstracts A novel heterogenous Co 3 O 4 -nanocube/Co(OH) 2 -nanosheet hybrid is prepared by a controllable facile one-pot hydrothermal reaction. The resulting Co 3 O 4 nanocubes are highly uniform in morphology, and are distributed uniformly on the individual Co(OH) 2 nanosheets. Such unique nanostructural features show significant advantages for applications as flexible supercapacitor electrodes in terms of enhanced durability and capacitance. The as-prepared electrode has offered a large capacitance of 1164 F g −1 at 1.2 A g −1 . When being paired with activated carbon, the resulting flexible all-solid-state device exhibited a maximum energy density of 9.4 mWh cm −3 . It is worthwhile noting that this as-assembled device showed little capacitance decay after over 5000 cycles with 97.4% retention of its original specific capacitance. Such a high performance outperforms most metal oxides-based electrodes and shows the advantages of the hybrid strategy, which shed light on exploring robust and cheap electrode materials for high-performance flexible supercapacitors.