Battery-type and binder-free MgCo2O4-NWs@NF electrode materials for the assembly of advanced hybrid supercapacitors

In this study, the hetero-structure of MgCo₂O₄ nanowires (MCO-NWs) and microcubes (MCO-MCs) on the skeleton of nickel foam (NF) was realized through a simple hydrothermal method and subsequent annealing treatment, and then served as a binder-free cathode for assembly of high-performance hybrid supercapacitor (HSC). Such synthetic methodology avoided the traditional usage of conductive and binder reagents for the electrode fabrication. The electrochemical tests indicated its battery-type characteristics, and the MCO-NWs@NF exhibited a huge specific capacity (C_s) of 389.0 C g^?1 as well as 86.2% capacity retention when the current density boosted from 1 to 10 A g^?1. The assembled HSC with activated carbon (AC) as anode further demonstrated the advantages of this electrode material. After 5000 cycles at 6 A g^?1, the MCO-NWs@NF//AC HSC showed good long-term cycling stability without any decay in capacitance, and could deliver an energy density (E_d) of 37.9 W h kg^?1 at the power density (P_d) of 958.1 W kg^?1, higher than the 30.4 W h kg^?1 of MCs-based HSC. These impressive results regarding electrochemical performance suggest that MCO-NWs@NF may be a promising candidate to serve as a battery-type material in electrochemical energy storage applications such as HSCs, batteries, and so on.     

Fabrication of core-shell NiMoO4@MoS2 nanorods for high-performance asymmetric hybrid supercapacitors

In this work, core-shell NiMoO₄@MoS₂ nanorods were successfully fabricated via a facile two-step hydrothermal method. By inheriting the merits of high electrical conductivity from MoS₂ nanosheets and high pseudocapacitive activity from NiMoO₄ nanorods, the hierarchical NiMoO₄@MoS₂ nanocomposite was endowed with improved electrical conductivity, enlarged specific surface area and enriched porosity, consequently enabling fast ion/electron transport and rapid Faradaic reactivity. Benefited from the synergism of NiMoO₄ and MoS₂, the NiMoO₄@MoS₂ electrode was superior to the NiMoO₄ and MoS₂ electrode, achieving specific capacitance of 2246.7 F g⁻¹, as well as showing good rate performance and improved cyclic stability (88.4% capacitance retention after 5000 cycles). The asymmetric supercapacitor device composed of the NiMoO₄@MoS₂ nanorods and hierarchical porous carbon exhibited a high energy density of 47.5 Wh kg⁻¹ at a power density of 0.44 kW kg⁻¹. The device also showed superior long-term cycling stability, retaining 80.2% of initial capacitance after 10 000 cycles. This work provides a simple strategy for scalable synthesis of integrated nanostructures, which holds great promise for the development of advanced supercapacitors.     

Metal-organic frameworks supported Ni–Co–S nanosheet arrays for advanced hybrid supercapacitors

Constructing self-supporting porous electrode material with abundant electrochemical active sites can effectively improve the energy storage capacity of supercapacitors. Herein, a novel electrode material (NCS@Co-ZIF/NF) is developed by depositing zeolitic imidazolate frameworks (Co-ZIF) on nickel foams (NF), which is adopted as a precursor (Co-ZIF/NF) to electrodeposit nickel-cobalt sulfides (NCS). The nanosheet arrays with cross-porous structures provide NCS@Co-ZIF/NF with excellent electrochemical characteristics, including a high specific capacity of 144.4 mAh g^?1 at the current density of 1 mA cm^?2, 60.5% capacity retention at 50 mA cm^?2, and superb long-term cycle stability. Furthermore, NCS@Co-ZIF/NF//AC hybrid supercapacitor is fabricated by using NCS@Co-ZIF/NF as positive electrodes and activated carbon (AC) as negative electrodes, which exhibits a high energy density of 33.9 Wh kg^?1 at a power density of 145 W kg^?1.     

Ni@NC@NiCo-LDH nanocomposites from a sacrificed template Ni@NC@ZIF-67 for high performance supercapacitor

A metal porous carbon (Ni@NC) supported nickel/cobalt layered double hydroxide (NiCo-LDH) (Ni@NC@NiCo-LDH) with a cauliflower morphology was synthesized by a successive double template method. At first a nickel metal-organic framework (Ni-MOF) was prepared and used as a sacrifice template to produce metal porous carbon (Ni@NC). Then the prepared conductive porous carbon material was exploited as a substrate for in-situ growing of ZIF-67 on its surface. Lastly the obtained Ni@NC@ZIF-67 was further used as a sacrifice template to prepare the final electrode material Ni@NC@NiCo-LDH by Ni²⁺ etching and co-precipitation. The cooperation of Ni@NC with excellent conductivity and NiCo-LDH with superior pseudocapacitive property yielded a synergistic effect, which effectively improved the electrochemical performance of the resulted electrode material. And the special flower morphology exposed more redox active sites and provided proper charge transport path for enhanced electrochemical performance. The prepared Ni@NC@NiCo-LDH exhibited a high specific capacitance of 1761.8 F·g^?1 at the current density of 1 A·g^?1. The assembled Ni@NC@NiCo-LDH//AC asymmetric supercapacitor also displayed an acceptable energy density (39.27 Wh·kg^?1 at the power density of 757.21 W·kg^?1) and ultrahigh cycling stability (94.74% capacitance retention after 25000 cycles at 10 A g^?1).     

Simple synthesis of honeysuckle-like CuCo2O4/CuO composites as a battery type electrode material for high-performance hybrid supercapacitors

In this paper, porous CuCo₂O₄/CuO composites with novel honeysuckle-like shape (CuCo₂O₄/CuO HCs) have been prepared for the first time by a simple hydrothermal method and followed with an additional annealing process in air. The unique CuCo₂O₄/CuO HCs consisted of dense and slender petals with length of 1.3–1.5 μm and width of about 50 nm, and possessed a specific surface area of 36.09 m² g^?1 with main pore size distribution at 10.63 nm. When used as the electrode materials for supercapacitors, the CuCo₂O₄/CuO HCs exhibited excellent electrochemical performances with a high specific capacity of 350.69 C g^?1 at 1 A g^?1, a rate capability of 78.6% at 10 A g^?1, and 96.2% capacity retention after 5000 cycles at a current density of 5 A g^?1. In addition, a hybrid supercapacitor (CuCo₂O₄/CuO HCs//AC HSC) was assembled using the CuCo₂O₄/CuO HCs as positive electrode and activated carbon (AC) as negative electrode. The HSC device delivered a specific capacity of 187.85 C g^?1 at 1 A g^?1 and a superior cycling stability with 104.7% capacity retention after 5000 cycles at 5 A g^?1, and possessed a high energy density of 41.76 W h kg^?1 at a power density of 800.27 W kg^?1. These outstanding electrochemical performances manifested the great potential of CuCo₂O₄/CuO HCs as a promising battery-type electrode material for the next-generation advanced supercapacitors with high-performance.     

Designing a hierarchical structure of nickel-cobalt-sulfide decorated on electrospun N-doped carbon nanofiber as an efficient electrode material for hybrid supercapacitors

The intent of designing and exploring novel active electrode materials is to enhance the electrochemical performance of supercapacitors. Herein, a hierarchical structure of nickel-cobalt-sulfide nanostructures (NiCo₂S₄) decorated on the electrospun N-doped carbon nanofiber (CNF), NiCo₂S₄@CNF, is manipulated using a one-step and simple hydrothermal approach. The fabricated hierarchical structure of the NiCo₂S₄@CNF is featured by a large surface area and a high porosity that serve as ion diffusion channels. Therefore, it manifests high specific capacitance and specific capacity values of 377.2 C g^?1 and 754.4 F g^?1 at a current density of 1 A g^?1, respectively. Furthermore, a NiCo₂S₄@CNF//CNF hybrid supercapacitor in which a positive electrode of NiCo₂S₄@CNF is assembled with a negative electrode of CNF to estimate the electrochemical performance of the NiCo₂S₄@CNF. As a result, the device has a superior energy density of 65.6 and 52.5 Wh kg^?1 at a power density of 665 and 1313.8 W kg^?1, respectively. Moreover, the device reveals good stability with capacitance retention of 72% after 3000 charge/discharge cycles. These outstanding results enable the designed hierarchical structure of the NiCo₂S₄@CNF to be a promising electrode material for supercapacitors (SCs) applications.     

Interconnected NiS-nanosheets@porous carbon derived from Zeolitic-imidazolate frameworks (ZIFs) as electrode materials for high-performance hybrid supercapacitors

Nickel sulfide-based materials have shown great potential for electrode fabrication owing to their high theoretical specific capacitance but poor conductivity and morphological aggregation. A feasible strategy is to design hybrid structure by introducing highly-conductive porous carbon as the supporting matrix. Herein, we synthesized hybrid composites consisting of interconnected NiS-nanosheets and porous carbon (NiS@C) derived from Zeolitic-imidazolate frameworks (ZIFs) using a facile low-temperature water-bath method. When employed as electrode materials, the as-prepared NiS@C nanocomposites present remarkable electrochemical performance owing to the complex effect that is the combined advantages of double-layer capacitor-type porous carbon and pseudocapacitor-type interconnected-NiS nanosheets. Specifically, the NiS@C nanocomposites exhibit a high specific capacitance of 1827 F g⁻¹ at 1 A g⁻¹, and excellent cyclic stability with a capacity retention of 72% at a very high current density of 20 A g⁻¹ after 5000 cycles. Moreover, the fabricated hybrid supercapacitor delivers 21.6 Wh kg⁻¹ at 400 W kg⁻¹ with coulombic efficiency of 93.9%, and reaches 10.8 Wh kg⁻¹ at a high power density of 8000 W kg⁻¹, along with excellent cyclic stability of 84% at 5 A g⁻¹ after 5000 cycles. All results suggest that NiS@C nanocomposites are applicable to high-performance electrodes in hybrid supercapacitors and other energy-storage device applications.     

Chicken nuggets-like core/shell nanosheet arrays as high performance flexible all-solid-state supercapacitor cathode and buckwheat shell as anode

The energy density of a flexible all-solid-state supercapacitor (ASC) requires new electrode material with special structure and morphology as a prerequisite for its secured improvement. In this paper, a new morphological exploration of chicken nuggets-like core/shell NiCo₂O₄/MnO₂ (NCM) nanosheet arrays on Ni foam was employed. The application of this special morphology aims to greatly improve the electrochemical performance of the cathode electrode. Additionally, Buckwheat Biochar (BBC) is utilized as the anode while the PVA/KOH thin film is prepared as the separator. The chicken nuggets-like core/shell NCM nanosheet arrays were obtained by a two-step hydrothermal method. A series of characterization methods were carried out to further support the core/shell's well-designed structure and precise composition. The tests exhibited excellent specific capacitance of 593.3 F g^?1 at 5 mA cm^?2 and outstanding cycling stability with a retention of 90% after 10000 cycles. Furthermore, the assembled NCM//BBC ASC device indicated a high specific capacitance (239 F g^?1 at the current density of 5 mA cm^?2), this is in due part of the unique architecture of NCM nanosheet arrays and interconnected special porous structure of the BBC and the thin film PVA/KOH. Hence, the assembled ASC device exhibited high energy density (an energy density of 58 Wh·kg^?1 at 3263 W kg^?1) and remarkable cycling stability.     

Controlled growth of hierarchical FeCo2O4 ultrathin nanosheets and Co3O4 nanowires on nickle foam for supercapacitors

In recent years, the tenable design and synthesis of the core/shell heterostructure as electrode for the supercapacitor, have attained a huge attention and concerns. In this article, the three-dimensional heterostructure consisting of FeCo₂O₄ ultrathin nanosheets grown on the space of vertical Co₃O₄ nanowires has been designed and synthesized onto nickel foam (NF) for pseudocapacitive electrode applications. According to previous research, the NF@ FeCo₂O₄ electrodes can only exhibit specific capacity of 1172 F g⁻¹ at a current density of 1 A g⁻¹. In addition, although the capacity of the NF@Co₃O₄ electrodes can reach to 1482 F g⁻¹ and it has the disadvantage of agglomeration, which restricts the diffusion of ions and has a negative effect on the progress of electrochemical reactions. Therefore, a core-shell nanostructure is fabricated by an improved two-step hydrothermal process, which improves the probability of ion reaction with more efficient charge transfer. Furthermore, in as-prepared unique core/shell heterostructure, the resultant electrode possesses the merits of large capacitance of 1680 F g⁻¹ at a current density of 1 A g⁻¹, an excellent rate capability of 70.1% at 20 A g⁻¹ and only 9.8% loss of initial capacitance at a high charge/discharge current density after 2000 cycles. These results demonstrate that this kind of distinct electrode has potential utilization for supercapacitor.     

The P/NiFe doped NiMoO4 micro-pillars arrays for highly active and durable hydrogen/oxygen evolution reaction towards overall water splitting

Water splitting is an efficient strategy to produce purity hydrogen and convert intermittent electricity from renewable wind and solar sources. In this work, dense NiMoO₄ micro-pillars arrays (MPAs) were in-situ grown on nickel foam (NF) through facile hydrothermal method, then the NiMoO₄/NF were converted into NiMoO₄–P/NF and NiFe/NiMoO₄/NF via phosphating and electrodeposition method, respectively. The NiMoO₄–P/NF electrode required small overpotentials of 34 mV@10 mA cm⁻² and 130 mV@100 mA cm⁻² for hydrogen evolution reaction (HER). The NiFe/NiMoO₄/NF electrode exhibited excellent oxygen evolution reaction (OER) activity with overpotentials of 210 mV@10 mA cm⁻² and 300 mV@100 mA cm⁻². The overall water splitting using the anode-cathode couple of NiFe/NiMoO₄/NF||NiMoO₄–P/NF only consumes low voltages of 1.47 V@10 mA cm⁻² for 100 h and 1.66 V@100 mA cm⁻² for 50 h in 1 M KOH. The electronic modification and the well-designed hierarchical structure contribute the high energy-efficient and stabile overall water splitting.     

Polyaniline-silver-manganese dioxide nanorod ternary composite for asymmetric supercapacitor with remarkable electrochemical performance

Metal oxide incorporated with a conductive polymer have shown great potential as high-performance energy storage devices. In this report, polyaniline wrapped silver decorated manganese dioxide (PANI/Ag@MnO₂) nanorods were successfully synthesized and used as positive electrode material. Cyclic voltammetry, galvanostatic charge discharge and electrochemical impedance spectroscopy were employed to investigate the electrochemical activities. The overall result demonstrates that as prepared PANI/Ag@MnO₂ nanorod performed better supercapacitor activities compared to Ag@MnO₂ and pure MnO₂. The PANI/Ag@MnO₂ nanocomposite exhibited a high specific capacitance of 1028.66 F g^?1 at a current density of 1 A g^?1 (nearly close to the theoretical capacitance of MnO₂). A detail investigation of the synergic effect of PANI, Ag and MnO₂ on electrochemical properties is presented sequentially. The assembled (PANI/Ag@MnO₂//AC) asymmetric supercapacitor device showed a high energy density of 49.77 W h kg^?1 at power density of 1599.75 W kg^?1. The facile and cost-effective production of PANI/Ag@MnO₂ demonstrates a high specific capacitance and energy density with long life cycle introduces this material as a prospective candidate for energy management.     

Nickel-cobalt layered double hydroxide ultrathin nanosheets coated on reduced graphene oxide nonosheets/nickel foam for high performance asymmetric supercapacitors

Here in, for the first time, we report a new and simple procedure for preparing reduced graphene oxide/nickel-cobalt double layered hydroxide composite on the nickel foam (Ni-Co LDH/rGO/NF) via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of CTAB as a cationic surfactant. Graphene oxide coated nickel foam prepared by simple immersion method. After that, the prepared electrode reduced electrochemically to obtain rGO/NF electrode. Finally, the rGO/NF electrode was used as cathode for electrodeposition of Ni-Co LDH in the presence of CTAB as cationic surfactant. The prepared electrodes were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDS), Brunauer, Emmett and Teller (BET) and electrochemical techniques such as voltammetry (CV), galvanostatic charge-discharge curves (GCD) and electrochemical impedance spectroscopy (EIS). The resulting electrode which prepared in the presence of CTAB afforded extremely high specific capacitance of 2133.3 F g^?1 at a current density of 4 A g^?1. FE-SEM, TEM and EDS mapping results showed that Ni-Co LDH nanosheets uniformly covered the surface of rGO/NF in the presence of CTAB, and is closely packed and thinner in thickness compared with the sample prepared in similar way without using surfactant. Such new thin and dense morphology facilitates electrolyte ions diffusion through the prepared electrode. A good cycling stability was obtained for the electrode in alkaline media. EIS measurements showed low values of internal resistance (R_s) and charge transfer resistance (R_ct), indicating that the prepared nanocomposite is a promising candidate for supercapacitor applications. The asymmetric supercapacitor (ASC) based on the Ni-Co LDH/CTAB/rGO/NF as a positive electrode and rGO/NF as a negative electrode was assembled and it exhibited a C_s of 71.4 F g^?1 at a current density of 2 A/g and correspondingly energy density of as high as 68 Wh kg^?1.     

Binder-free engineering design of Ni-MOF ultrathin sheet-like grown on PANI@GO decorated nickel foam as an electrode for in hydrogen evolution reaction and asymmetric supercapacitor

In this study, Ni₃(benzene 1,3,5-tricarboxylic acid)@polyaniline-rGO nanocomposite (Ni-MOF@PANI-rGO) is fabricated by a two-step procedure involving polymerization and hydrothermal operations. This nanocomposite-based Ni-MOF was designed for binder-free surface modification of nickel foam (NF). This is offered a novel approach for enhancing the electrochemical performance, and even energy density with a wider operating potential window. An in-situ Ni-MOF was then synthesized on polyaniline@GO (PANI-GO) using an NH-fragment linker and an in-situ hydrothermal technique. The electrochemical behavior of the nanocomposite was studied in asymmetric systems and exhibited outstanding electrochemical performance, high energy density, and power density (73.99 Wh kg⁻¹ at 848.29 W kg⁻¹). The electrode also showed a high specific capacity (1680 C g⁻¹ at 1.0 A g⁻¹) and exceptional cycling stability (92⁒) after 5000 cycles in a three-electrode system. The present results imply a direct application of Ni-MOF@PANI-rGO composite as a bridge performance between supercapacitors and batteries. In addition, the electrocatalyst activity of Ni-MOF@PANI-rGO toward hydrogen evolution reaction (HER) was investigated by linear sweep voltammetry at a scan rate of 10 mV s⁻¹ in 1.0 M KOH. The results showed that Ni-MOF@PAN-rGO acts as a suitable electrocatalyst with the lowest overpotential at 10, 50, and 80 mA cm⁻² and the lowest Tafel slope.     

Co-precipitation synthesis of nickel cobalt hexacyanoferrate for binder-free high-performance supercapacitor electrodes

Prussian blue analogue with a typical metal-organic framework has been widely used as an electrode material in supercapacitor. In this work, nickel cobalt hexacyanoferrate (Ni₂CoHCF) was grown on nickel foam directly using a simple co-precipitation method. The as-prepared Ni₂CoHCF was tested by transmission electron microscope, scanning electron microscope, X-ray diffraction and X-ray electron energy spectrum. The results showed that Ni₂CoHCF has a unique open face-centered cubic structure. The Ni₂CoHCF was used to set an asymmetric supercapacitor directly. A series of electrochemical tests showed that Ni₂CoHCF had an excellent electrochemical performance. The specific capacitance of the supercapacitor was 585 C g⁻¹ (1300.0 F g⁻¹, 162.5 mAh g⁻¹) at the current density of 0.5 A g⁻¹. After 2000 cycles, it still maintained 85.57% of its initial specific capacitance at the current density of 10 A g⁻¹. The energy density was 30.59 Wh kg⁻¹ at the power density of 378.7 W kg⁻¹. The results show that the supercapacitor constructed by Ni₂CoHCF as an electrode material has high-current charge-discharge capacity, high energy density and long cycle life.     

Facile preparation of SnS2 nanoflowers and nanoplates for the application of high-performance hybrid supercapacitors

In this work, the SnS₂ nanoflowers (SnS₂ NFs) were solvothermally prepared in the solvent of ethanol, while SnS₂ nanoplates (SnS₂ NPs) were obtained through the identical conditions except for the solvent of water. The flowers were assembled with numerous nanosheets with very thin thickness, and the NPs exhibited hexagonal shape. When used as the battery-type electrode material for supercapacitors, the SnS₂ NFs delivered a specific capacity of as high as 264.4 C g^?1 at 1 A g^?1, which was higher than the 201.6 C g^?1 of SnS₂ NPs. Furthermore, a hybrid supercapacitor (HSC) was assembled with the SnS₂ as positive electrode and activated carbon (AC) as negative electrode, respectively. The SnS₂ NFs//AC HSC exhibited a high energy density of 28.1 Wh kg^?1 at 904.3 W kg^?1, which was higher than the 24.2 Wh kg^?1 at 844.3 W kg^?1 of SnS₂ NPs//AC HSC. Especially, when the power density was enhanced to the highest value of 8666.8 W kg^?1, the NFs-based device could still hold 20.4 Wh kg^?1. In addition, both HSC devices showed an excellent cycling stability after 5000 cycles at 5 A g^?1. The present method is simple and can be extended to the preparation of other transition metal sulfides (TMSs)-based electrode materials with brilliant electrochemical performance for supercapacitors.     

Electrospun NiO/C nanofibers as electrode materials for hybrid supercapacitors with superior electrochemical performance

In this work, the porous NiO/C nanofibers (NFs) were rationally designed and prepared by a convenient electrospinning method, and followed with a calcination conversion of the precursor in air. The NiO/C composite exhibited a net-like structure that was composed of many intertwined NFs with an average diameter of about 200 nm. The electrochemical measurements demonstrated that the porous NiO/C NFs exhibited an electrochemical feature of battery-type electrode material, and delivered a specific capacity as high as 461.26 C g^?1 under 1 A g^?1 and an excellent rate capability with 82.7% capacity retention at 10 A g^?1. A hybrid supercapacitor (NiO/C NFs//AC HSC) was assembled with NiO/C NFs as positive electrode and activated carbon (AC) as negative electrode, which delivered an energy density of 31.82 W h kg^?1 under a power density of 816.36 W kg^?1 along with an outstanding cyclic stability of 90.9% capacity retention over 5000 cycles at 5 A g^?1. This simple synthetic method can be extended to the fabrication of other transition metal oxides (TMOs)-based NFs for their further applications in high-performance electrochemical energy storage devices such as hybrid supercapacitors, batteries, and so on.     

Nickel–cobalt layered double hydroxide/NiCo2S4/g-C3N4 nanohybrid for high performance asymmetric supercapacitor

Graphitic carbon nitride (g-C₃N₄) with semiconducting nature can be considered for energy storage system by modifying its electrical conductivity and structural properties through formation of hybrid with materials such as bimetallic metal sulfide and nickel-cobalt layered double hydroxide (LDH). g-C₃N₄ as a N-rich compound with basic surface sites can change the surface properties of nanohybrid and impress the charge transfer. In this study, a nanohybrid based on nickel-cobalt LDH and sulfide and graphitic carbon nitride (NiCo LDH/NiCo₂S₄/g-C₃N₄) was synthesized through a three-step method. At first, Ni doped ZIF-67 was formed at the surface of g-C₃N₄ nanosheets and then the product was calcined in a furnace to form NiCo₂O₄/g-C₃N₄. At next step, the sample was hydrothermally converted to NiCo₂S₄/g-C₃N₄ using thioacetamide and finally modified with NiCo LDH nanoplates to form porous structure with high surface area. The NiCo LDH/NiCo₂S₄/g-C₃N₄ nanohybrid showed high specific capacitance of 1610 F g^?1 at current density of 1 A g^?1 and also excellent stability of 108.8% after 5000 cycles at potential scan rate of 50 mV s^?1, which makes it promising candidate for energy storage. An asymmetric system was prepared using nickel foams modified with NiCo LDH/NiCo₂S₄/g-C₃N₄ and g-C₃N₄ as positive and negative electrodes, respectively. The specific capacitance of 246.0 F g^?1 was obtained at 1 A g^?1 in 6 M KOH solution and system maintained 90.8% cyclic stability after 5000 cycles at potential scan rate of 50 mV s^?1. The maximum energy density and power density of the system were calculated as 82.0 Wh kg^?1 and 12,000 W kg^?1, respectively, which demonstrate its capability for energy storage.     

Rational design of hierarchical core-shell structured CoMoO4@CoS composites on reduced graphene oxide for supercapacitors with enhanced electrochemical performance

Engineering multicomponent active materials as an advanced electrode with the rational designed core-shell structure is an effective way to enhance the electrochemical performances for supercapacitors. Herein, three-dimensional self-supported hierarchical CoMoO₄@CoS core-shell heterostructures supported on reduced graphene oxide/Ni foam have been rationally designed and prepared via a facile approach. The unique structure and the synergistic effects between two different materials, as well as excellent electronic conductivity of the reduced graphene oxide, contribute to the increased electrochemically active site and enhanced capacitance. The core-shell CoMoO₄@CoS composite displays the superior specific capacitance of 3380.3 F g⁻¹ (1 A g⁻¹) in the three-electrode system and 81.1% retention of the initial capacitance even after 6000 cycles. Moreover, an asymmetric device was successfully prepared using CoMoO₄@CoS and activated carbon as positive/negative electrodes. It is worth mentioning that the device delivered the high energy density of 59.2 W h kg⁻¹ at the power density of 799.8 W kg⁻¹ and the excellent cycle performance (about 91.5% capacitance retention over 6000 cycles). These results indicate that the core-shell CoMoO₄@CoS composites offers the novelty strategy for preparation of electrodes for energy conversion and storage devices.     

Facile fabrication of comb-like porous NiCo2O4 nanoneedles on Ni foam as an advanced electrode for high-performance supercapacitor

It is very desirable to develop the high-performance supercapacitors to meet the rapidly growing demands for energy-autonomous operation and miniaturization of devices. Herein, comb-like porous NiCo₂O₄ nanoneedles on the three-dimension (3D) nickel foam (NF) have been successfully synthesized through a facile pulsed laser ablation (PLA) approach without any post-treatments and surfactant (denoted as NiCo₂O₄-PLA). The influence of working solution during the fabricated process on the properties of NiCo₂O₄-PLA has been demonstrated in detail in terms of the crystalline structure, specific surface area, morphology, and electrochemical performance. Benefiting from the large specific surface (261.4 m² g⁻¹), abundant pores, and highly conductive scaffold, the NiCo₂O₄-PLA binder-free electrode exhibits an outstanding specific capacitance (1650 F g⁻¹ at a current density of 1 A g⁻¹) and eminent cycling performance (91.78% retention after a 12,000-cycle test at a current density of 10 A g⁻¹) compared with the control samples. The assembled asymmetric device (NiCo₂O₄-PLA//AC-ASCs) delivers the high specific capacitance of 126.9 F g⁻¹ at the current density of 1 A g⁻¹, the large energy density of 56.7 Wh kg⁻¹ at a power density of 756 W kg⁻¹, and the low internal resistance. The attractive results strongly prove that it is an ideal candidate for advanced supercapacitor application.     

Microwave-synthesized self-supporting CoSe2/carbon fiber felt electrode for ultra–high cycling life flexible supercapacitors

Flexible electrodes are candidate for portable and wearable electronic storage devices. In this work, high-performance flexible self-supporting CoSe₂/carbon fiber felt (CoSe₂/CFF) electrode was prepared via the microwave method without any binder. The CoSe₂/CFF electrodes exhibited superior electrochemical performance (621 F g^?1 at 1 A g^?1) and an ultra-high cycling life (84.7% capacitance retention after 100,000 cycles). When the CoSe₂/CFF was used as the positive electrode for the flexible supercapacitor, the assembled device exhibited an outstanding energy density of 22.43 W h Kg^?1 at a power density of 823.12 W kg^?1. Because of the excellent mechanical stability of the device, it maintained 91.3% of its initial C after bending from 0° to 180°. The CoSe₂/CFF proposed in this work shows electrode promising applicability to a low-cost, small-sized wearable and portable energy storage device.