Nickel-based bimetallic battery-type materials for asymmetric supercapacitors

Fabrication of a vanadium-doped Ni-MOF with a hydrangea-like morphology as an electrode for high-performance supercapacitors

In this work, we successfully fabricated a vanadium-doped Ni-MOF (NiV-MOF) with a three-dimensional hydrangea-like morphology via a simple one-pot hydrothermal synthesis method. As an electrode material, the Ni0.9V0.1-MOF demonstrated superior performance, achieving a specific capacitance of 1182 F g-1 at a current density of 1 A g-1.

Extrinsic Pseudocapacitive CoOOH Achieved by the Suppression of Its Phase Transition Triggered by S2- Doping

The behavior transformation of battery-type materials to extrinsic pseudocapacitive behavior is accomplished by suppressing their phase transition. The resulting extrinsic pseudocapacitive materials are a valuable supplement to intrinsic pseudocapacitive materials, enriching the connotation of pseudocapacitive materials. Nevertheless, the research on this category of materials remains inactive as of now, probably due to the as yet unclear phase transition suppression mechanism and the associated electrochemical mechanism. In this work, the battery-type Co(OH)2 is selected as a research object to create an extrinsic pseudocapacitive material by S2- doping. It is revealed that the K+ intercalation/deintercalation is the essential reason for the phase transition of CoOOH that is irreversibly converted from Co(OH)2, leading to its battery-type behavior. Whereas, the fully protonated CoOOH produced due to the high reaction activity of S2- doped Co(OH)2 only allows the intercalation/deintercalation of H+. During the process of intercalation/deintercalation of H+, CoOOH retains the P3 structure, thereby giving rise to extrinsic pseudocapacitive behavior. The electrochemical measurement results indicate that this extrinsic pseudocapacitive material and the assembled device have electrochemical performance equivalent to that of intrinsic pseudocapacitive materials.

Optical detection strategies for Ni(II) ion using metal-organic chemosensors: from molecular design to environmental applications

Nickel is an important element utilized in various industrial/metallurgical processes, such as surgical and dental prostheses, Ni-Cd batteries, paint pigments, electroplating, ceramics, computer magnetic tapes, catalysis, and alloy manufacturing. However, its extensive use and associated waste production have led to increased nickel pollution in soils and water bodies, which adversely affects human health, animals and plants. This issue has prompted researchers to develop various optical probes, hereafter luminescent/colorimetric sensors, for the facile, sensitive and selective detection of nickel, particularly in biological and environmental contexts. In recent years, numerous functionalized chemosensors have been reported for imaging Ni2+, both in vivo and in vitro. In this context, metal-based receptors offer clear advantages over conventional organic sensors (viz., organic ligands, polymers, and membranes) in terms of cost, durability, stability, water solubility, recyclability, chemical flexibility and scope. This review highlights recent advancements in the design and fabrication of hybrid receptors (i.e., metal complexes and MOFs) for the specific detection of Ni2+ ions in complex environmental and biological mixtures.

2D-on-2D Al-Doped NiCo LDH Nanosheet Arrays for Fabricating High-Energy-Density, Wide Voltage Window, and Ultralong-Lifespan Supercapacitors

Battery-type electrode materials with high capacity, wide potential windows, and good cyclic stability are crucial to breaking through energy storage limitations and achieving high energy density. Herein, a novel 2D-on-2D Al-doped NiCo layered double hydroxide (NiCoAlx LDH) nanosheet arrays with high-mass-loading are grown on a carbon cloth (CC) substrate via a two-step hydro/solvothermal deposition strategy, and the effect of Al doping is employed to modify the deposition behavior, hierarchical morphology, phase stability, and multi-metallic synergistic effect. The optimized NiCoAl0.1 LDH electrode exhibits capacities of 5.43, 6.52, and 7.25 C cm-2 (9.87, 10.88, and 11.15 F cm-2) under 0-0.55, 0-0.60, and 0-0.65 V potential windows, respectively, illustrating clearly the importance of the wide potential window. The differentiated deposition strategy reduces the leaching level of Al3+ cations in alkaline solutions, ensuring excellent cyclic performance (108% capacity retention after 40 000 cycles). The as-assembled NiCoAl0.1 LDH//activated carbon cloth (ACC) hybrid supercapacitor delivers 3.11 C cm-2 at 0-2.0 V, a large energy density of 0.84 mWh cm-2 at a power density of 10.00 mW cm-2, and excellent cyclic stability with ≈135% capacity retention after 150 000 cycles.

Recent Development on Transition Metal Oxides-Based Core-Shell Structures for Boosted Energy Density Supercapacitors

In recent years, nanomaterials exploration and synthesis have played a crucial role in advancing energy storage research, particularly in supercapacitor development. Researchers have diversified materials, including metal oxides, chalcogenides, and composites, as well as carbon materials, to enhance energy and power density. Balancing energy density with electrochemical stability remains challenging, driving intensified efforts in advancing electrode materials. This review focuses on recent progress in designing and synthesizing core-shell materials tailored for supercapacitors. The core-shell architecture offers advantages such as increased surface area, redox active sites, electrical conductivity, ion diffusion kinetics, specific capacitance, and cyclability. The review explores the impact of core and shell materials, specifically transition metal oxides (TMOs), on supercapacitor electrochemical behavior. Metal oxide choices, such as cobalt oxide as a preferred core and manganese oxide as a shell, are discussed. The review also highlights characterization techniques for assessing structural, morphological, and electrochemical properties of core-shell materials. Overall, it provides a comprehensive overview of ongoing TMOs-based core-shell material research for supercapacitors, showcasing their potential to enhance energy storage for applications ranging from gadgets to electric vehicles. The review outlines existing challenges and future opportunities in evolving TMOs-based core-shell materials for supercapacitor advancements, holding promise for high-efficiency energy storage devices.

Designing transition metal-based porous architectures for supercapacitor electrodes: a review

Over the past decade, transition metal (TM)-based electrodes have shown intriguing physicochemical properties and widespread applications, especially in the field of supercapacitor energy storage owing to their diverse configurations, composition, porosity, and redox reactions. As one of the most intriguing research interests, the design of porous architectures in TM-based electrode materials has been demonstrated to facilitate ion/electron transport, modulate their electronic structure, diminish strain relaxation, and realize synergistic effects of multi-metals. Herein, the recent advances in porous TM-based electrodes are summarized, focusing on their typical synthesis strategies, including template-mediated assembly, thermal decomposition strategy, chemical deposition strategy, and host-guest hybridization strategy. Simultaneously, the corresponding conversion mechanism of each synthesis strategy are reviewed, and the merits and demerits of each strategy in building porous architectures are also discussed. Subsequently, TM-based electrode materials are categorized into TM oxides, TM hydroxides, TM sulfides, TM phosphides, TM carbides, and other TM species with a detailed review of their crystalline phase, electronic structure, and microstructure evolution to tune their electrochemical energy storage capacity. Finally, the challenges and prospects of porous TM-based electrode materials are presented to guide the future development in this field.

Constructing Hierarchical CoGa2O4-S@NiCo-LDH Core-Shell Heterostructures with Crystalline/Amorphous/Crystalline Heterointerfaces for Flexible Asymmetric Supercapacitors

The rational design and construction of composite electrodes are crucial for overcoming the issues of poor working stability and slow ionic electron mobility of a single component. Nevertheless, it is a big challenge to construct core-shell heterostructures with crystalline/amorphous/crystalline heterointerfaces in straightforward and efficient methods. Here, we have successfully converted a portion of crystalline CoGa2O4 into the amorphous phase by employing a facile sulfidation process (denoted as CoGa2O4-S), followed by anchoring crystalline NiCo-layered double hydroxide (denoted as NiCo-LDH) nanoarrays onto hexagonal plates and nucleation points of CoGa2O4-S, synthesizing dual-type hexagonal and flower-like 3D CoGa2O4-S@NiCo-LDH core-shell heterostructures with crystalline/amorphous/crystalline heterointerfaces on carbon cloth. Furthermore, we further adjust the Ni/Co ratio in LDH, achieving precise and controllable core-shell heterostructures. Benefiting from the abundant crystalline/amorphous/crystalline heterointerfaces and synergistic effect among various components, the CoGa2O4-S@Ni2Co1-LDH electrode exhibits a specific capacity of 247.8 mAh·g-1 at 1 A·g-1 and good rate performance. A CoGa2O4-S@Ni2Co1-LDH//AC flexible asymmetric supercapacitor provides an energy density of 58.2 Wh·kg-1 at a power density of 850 W·kg-1 and exhibits an impressive capacitance retention of 105.7% after 10,000 cycles at 10 A·g-1. Our research provides profound insights into the design of other similar core-shell heterostructures.

Microwave Construction of NiSb/NiTe Composites on Ni-Foam for High-Performance Supercapacitors

In this paper, NiSb/NiTe/Ni composites were smoothly developed via the microwave method for supercapacitors. The synthesis of NiSb/NiTe crystals was revealed by X-ray photoelectron spectroscopy and X-ray diffraction. The analytic results of scanning electron microscopy and energy dispersive spectroscopy uncover the microscopic morphology as well as the constituent elements of the composites. Self-supported NiSb/NiTe is a supercapacitor cathode that combines high capacitance with excellent cycling stability. The obtained composite electrode displayed remarkable electrochemical properties, presenting a special capacitance of 1870 F g-1 (1 A g-1) and 81.5% of the original capacity through 30,000 times (10 A g-1) of the charging/discharging process. Further, an asymmetric supercapacitor was prepared employing NiSb/NiTe as a cathode and activated carbon as an anode. NiSb/NiTe//AC exhibited a high energy density of 224.6 uW h cm-2 with a power density of 750 μW cm-2 and provided a favorable cycling stability of 83% after 10,000 cycles.

Ultrafast Synthesis of Graphene-Embedded Cyclodextrin-Metal-Organic Framework for Supramolecular Selective Absorbency and Supercapacitor Performance

Limited by preparation time and ligand solubility, synthetic protocols for cyclodextrin-based metal-organic framework (CD-MOF), as well as subsequent derived materials with improved stability and properties, still remains a challenge. Herein, an ultrafast, environmentally friendly, and cost-effective microwave method is proposed, which is induced by graphene oxide (GO) to design CD-MOF/GOs. This applicable technique can control the crystal size of CD-MOFs from macro- to nanocrystals. CD-MOF/GOs are investigated as a new type of supramolecular adsorbent. It can selectively adsorb the dye molecule methylene green (MG) owing to the synergistic effect between the hydrophobic nanocavity of CDs, and the abundant O-containing functional groups of GO in the composites. Following high temperature calcination, the resulting N, S co-doped porous carbons derived from CD-MOF/GOs exhibit a high capacitance of 501 F g-1 at 0.5 A g-1 , as well as stable cycling stability with 90.1% capacity retention after 5000 cycles. The porous carbon exhibits good electrochemical performance due to its porous surface containing numerous electrochemically active sites after dye adsorption and carbonization. The design strategy by supramolecular incorporating a variety of active molecules into CD-MOFs optimizes the properties of their derived materials, furthering development toward the fabrication of zeitgeisty and high-performance energy storage devices.

Fluorescent and chromogenic organic probes to detect group 10 metal ions: design strategies and sensing applications

Group 10 metals including Ni, Pd and Pt have been extensively applied in various essential aspects of human social life, material science, industrial manufactures, medicines and biology. The ionic forms of these metals are involved in several biologically important processes due to their strong binding capability towards different biomolecules. However, the mishandling or overuse of such metals has been linked to serious contamination of our ecological system, more specifically in soil and water bodies with acute consequences. Therefore, the detection of group 10 metal ions in biological as well as environmental samples is of huge significance from the human health point of view. Related to this, considerable efforts are underway to develop adequately efficient and facile methods to achieve their selective detection. Optical sensing of metal ions has gained increasing attention of researchers, particularly in the environmental and biological settings. Innovatively designed optical probes (fluorescent or colorimetric) are usually comprised of three basic components: an explicitly tailored receptor unit, a signalling unit and a clearly defined reporter unit. This review deals with the recent progress in the design and fabrication of fluorescent or colorimetric organic sensors for the detection of group 10 metal ions (Ni(II), Pd(II) and Pt(II)), with attention to the general aspects for design of such sensors.

Mesoporous Iron Family Element (Fe, Co, Ni) Molybdenum Disulfide/Carbon Nanohybrids for High-Performance Supercapacitors

As the demand for fuel continues to increase, the development of energy devices with excellent performance is crucial. Supercapacitors (SCs) are attracting attention for their advantages of high specific energy and a long cycle life. At present, the development of high-performance electrode materials is the main point for research and development of SCs. Transition metal sulfides have the advantages of a large interlayer space and high theoretical capacity, making them promising electrode materials. Herein, we reported a series of ultrathin mesoporous iron family element (Fe, Co, Ni) molybdenum disulfide (MxMo1-xS2/C, M = Fe, Co, and Ni) by a template method. The original monolayer mesoporous structure of MoS2/C was maintained, and accumulation and agglomeration of MoS2/C were avoided. Based on our investigations, the best performance was that of CoxMo1-xS2/C nanohybrids. Furthermore, the concentrations of Co and Mo ions were modulated to obtain the best performance, in which Mo and Co ions were released at 1:1, 1:2, and 1:3 ratios and they were named CoxMo1-xS2/C-1, CoxMo1-xS2/C-2, and CoxMo1-xS2/C-3, respectively. Overall, these materials represent a significant improvement and show promise as high-performance SC electrode materials due to their enhanced capacitance and stability. At a current density of 0.5 A g-1, CoxMo1-xS2/C-2 has the optimal specific capacitance of 184 F g-1. CoxMo1-xS2/C-2 as an SC electrode exhibited better reversible capacity and cycling stability than MoS2/C, which is an improvement over MoS2/C regarding reversible capacity and cycling stability.

Waste dry cell derived photo-reduced graphene oxide and polyoxometalate composite for solid-state supercapacitor applications

In the modern era, realizing highly efficient supercapacitors (SCs) derived through green routes is paramount to reducing environmental impact. This study demonstrates ways to recycle and reuse used waste dry cell anodes to synthesize nanohybrid electrodes for SCs. Instead of contributing to landfill and the emission of toxic gas to the environment, dry cells are collected and converted into a resource for improved SC cells. The high performance of the electrode was achieved by exploiting battery-type polyoxometalate (POM) clusters infused on a reduced graphene oxide (rGO) surface. Polyoxometalate (K5[α-SiMo2VW9O40]) assisted in the precise bottom-up reduction of graphene oxide (GO) under UV irradiation at room temperature to produce vanadosilicate embedded photo-reduced graphene oxide (prGO-Mo2VW9O40). Additionally, a chemical reduction route for GO (crGO) was trialed to relate to the prGO, followed by the integration of a faradaic monolayer (crGO-Mo2VW9O40). Both composite frameworks exhibit unique hierarchical heterostructures that offer synergic effects between the dual components. As a result, the hybrid material's ion transport kinetics and electrical conductivity enhance the critical electrochemical process at the electrode's interface. The simple co-participation method delivers a remarkable specific capacity (capacitance) of 405 mA h g-1 (1622 F g-1) and 117 mA h g-1 (470 F g-1) for prGO-Mo2VW9O40 and crGO-Mo2VW9O40 nanocomposites alongside high capacitance retentions of 94.5% and 82%, respectively, at a current density of 0.3 A g-1. Furthermore, the asymmetric electrochromic supercapacitor crGO//crGO-Mo2VW9O40 was designed, manifesting a broad operating potential (1.2 V). Finally, the asymmetric electrode material resulted in an enhanced specific capacity, energy, and power of 276.8 C g-1, 46.16 W h kg-1, and 1195 W kg-1, respectively, at a current density of 0.5 A g-1. The electrode materials were tested in the operating of a DC motor.

Hierarchical Lotus-Seedpod-Derived Porous Activated Carbon Encapsulated with NiCo2S4 for a High-Performance All-Solid-State Asymmetric Supercapacitor

Converting biowaste into carbon-based supercapacitor materials provides a new solution for high-performance and environmentally friendly energy storage applications. Herein, the hierarchical PAC/NiCo2S4 composite structure was fabricated through the combination of activation and sulfuration treatments. The PAC/NiCo2S4 electrode garnered advantages from its hierarchical structure and hollow architecture, resulting in a notable specific capacitance (1217.2 F g-1 at 1.25 A g-1) and superior cycling stability. Moreover, a novel all-solid-state asymmetric supercapacitor (ASC) was successfully constructed, utilizing PAC/NiCo2S4 as the cathode and PAC as the anode. The resultant device exhibited exceptionally high energy (49.7 Wh kg-1) and power density (4785.5 W kg-1), indicating the potential of this biomass-derived, hierarchical PAC/NiCo2S4 composite structure for employment in high-performance supercapacitors.

Structurally-stable Mg-Co-Ni LDH grown on reduced graphene by ball-milling and ion-exchange for highly-stable asymmetric supercapacitor

As an electrode for energy storage, the inherently poor conductivity of metal hydroxides (MHs) can be improved by in situ growth of MHs on conductive carbon based substrates so that their performances on energy storage could be enhanced to a high level. However, the incompatibility of hydrophilic component (metal hydroxides) and hydrophobic counterpart (carbon based materials) makes it difficult to be accomplished. Herein, we presented a scalable and easy-operated strategy by ball-milling combined with ion-exchange technique to grow Mg-Co-Ni LDH (layered double hydroxides) on reduced graphene, in which ball-milling was utilized to disperse the staring material of magnesium acetate on graphene oxide (GO) to obtain the composite of Mg(Ac)₂/GO. The composite can be in situ transformed to MgO/reduced grapheme (rG) by following heat treatment. While, the ion-exchange reaction could enables the in situ growth of Mg-Co-Ni LDHs on the reduced graphene. The derived products (denoted as Mg-Co-Ni LDH/rG-x) owns nanosheet morphology, surface area of 59-115 m²/g, homogenous elements distribution. As electrode for supercapacitor, the maximum capacitance of 1204F/g@1.0 A/g was achieved and the corresponding asymmetric supercapacitor device shows a large energy density of 44.3 Wh/kg@800 W/kg. Particularly, a superlong cycling stability with 90.5% capacitance retention of the first cycle was attained after continuous charge/discharge for 20 000 cycles at current density of 5.0 A/g, promising great potential for practical energy storage application. The present strategy is simple and scalable that can be widely applied to the synthesis of various hydroxides/oxides or multi-component hydroxides/oxides on carbon substrates forming a composite structure, thus offers a great potential for broad application areas including catalysis, adsorption, energy storage, etc.

Solvent-induced structural regulation over Ni2P/CNT hybrids towards boosting the performance of supercapacitors

Although nickel-based phosphides have attracted increasing attention due to their good theoretical specific capacity, the poor rate capability weakness their advantage in electrochemical energy storage. It is, however, challenging to improve these issues by only adjusting composition. Here, we employ a synergistic strategy, both hybridizing with highly conductive materials and regulating morphology, to enhance the electrochemical performance of Ni₂P. Based on solvent-induced effects, flower/rod-like [CH₃NH₃][Ni(HCOO)₃] precursors hybridized with CNTs are prepared and then employed as templates to construct flower/rod-like Ni₂P/CNT hybrids via a gas-solid phosphorization method. Benefiting from the synergistic advantages of both structure and components, the flower-like Ni₂P/CNT hybrid, as an electrode materials for supercapacitor, exhibit outstanding specific capacitance of up to 1480 F g^-1 at 1 A g^-1, as well as improved rate capability. Additionally, the assembled asymmetric supercapacitor (Ni₂P/CNTs//AC, ASC) delivers a high capacitance retention of up to 83.5% after 5000 cycles at 10 A g^-1, and an expected energy density of 25.2 W h kg^-1 at a power density of 749.8 W kg^-1.

Ni-Co-Mn hydrotalcite-derived hierarchically porous sulfide for hybrid supercapacitors

Ternary transition metal sulfides have attracted much attention due to their superior electrochemical properties. Nevertheless, it is difficult to commercialize sulfides due to their intrinsic properties such as dull reaction kinetics and an insufficient number of active sites. Herein, a self-supporting porous NiCoMnS sulfide (NiCoMnS/NF) arrayed on nickel foam (NF) with 3D honeycomb-like structure was designed and prepared via a hydrothermal and post-sulfidation process. It was found that the 3D hierarchically network architecture, constructed by nanosheets with abundant cavities, endowed NiCoMnS/NF with a high specific area and rich ion/electron-transport channels, which facilitated ion/electron transfer and Faradaic reaction kinetic. The optimal NiCoMnS/NF exhibited a markedly improved electrochemical performance due to the merits of complementary multi-composition and unique 3D network structure with multi-level "superhighways". Furthermore, the NiCoMnS//AC device fabricated with NiCoMnS/NF cathode and activated carbon (AC) anode delivered an excellent specific charge and exceptional energy density. This work offers a reference for designing the structure of electrode materials.

Phase-Dependent Energy Storage Performance of the NixSey Polymorphs for Supercapacitor-Battery Hybrid Devices

Transition-metal chalcogenides have emerged as a promising class of materials for energy storage applications due to their earth abundance, high theoretical capacity, and high electrical conductivity. Herein, we introduce a facile and one-pot electrodeposition method to prepare high-performance nickel selenide Ni_xSe_y (0.5 ≤ x/y ≤ 1.5) nanostructures (specific capacity = 180.3 mA h g^-1 at 1 A g^-1). The as-synthesized nickel selenide (NS) nanostructure is however converted to other polymorphs of nickel selenide including orthorhombic NiSe₂, trigonal Ni₃Se₂, hexagonal NiSe, and orthorhombic Ni₆Se₅ over cycling. Interestingly, NiSe₂ and Ni₃Se₂ polymorphs that display a more metallic character and superior energy storage performance are the predominant phases after a few hundred cycles. We fabricated a hybrid device using activated carbon (AC) as a supercapacitor-type negative electrode and NS as a high-rate battery-type positive electrode (AC||NS). This hybrid device provides a high specific energy of 71 W h kg^-1, an excellent specific power of up to 31 400 W kg^-1, and exceptional cycling stability (80% retention of the initial capacity after 20 000 cycles). The higher energy storage performance of the device is a result of the development of high-performance NiSe₂ and Ni₃Se₂ polymorphs. Moreover, the reduction of the critical dimension of the NS particles to the nanoscale partially induces an extrinsic pseudocapacitive behavior that improves the rate capability and durability of the device. We also explored the origin of the superior energy storage performance of the NS polymorphs using density functional theory calculations in terms of the computed density of states around the Fermi level, electrical conductivity, and quantum capacitance that follows the trend NiSe₂ > Ni₃Se₂ > NiSe > Ni₆Se₅. The present study thus provides an appealing approach for tailoring the phase composition of NS as an alternative to the commonly used templated synthesis methods.

New nickel-rich ternary carbonate hydroxide two-dimensional porous sheets for high-performance aqueous asymmetric supercapattery

Transition metal carbonate hydroxides (M-CHs) are promising candidates for electrode materials in supercapattery, due to their low-cost preparation and high-energy features. However, they also suffer from ionic kinetics bottlenecks without efficient morphological design. Tailoring the chemical compositions and nanostructures of electrode materials to realize high performance is significant for meeting the current demand for electrical energy storage devices. Therefore, we present a simple hydrothermal method for constructing better electrochemically active M-CHs with ternary metal components and hierarchical nanostructures that are assembled by interwoven nanosheets. Benefiting from higher contents of Ni species and superior two-dimensional/three-dimensional (2D/3D) pore structures, the fabricated cobalt-nickel-zinc carbonate hydroxides with Co/Ni/Zn molar ratios of 2:3:1 (CoNiZn-231) delivered the best specific capacity of 1130.8 C g^-1 at 1 A g^-1, decent rate performance (67.2% in 1-10 A g^-1), and excellent cycling performance (92.6% over 10,000 cycles) in comparison with the majority of mono/bimetallic materials. Then, an alkaline hybrid (CoNiZn-231//activated carbon (AC)) device is developed, which shows a high energy density of 31.62 Wh kg^-1 at a power density of 646 W kg^-1 and an excellent capacity retention of 99.27% after 10,000 cycles. Herein, the rational design of trimetallic compositions and hierarchical structures of carbonate hydroxides is described, which provides good choices for the synthesis of high-performance electrode materials in electrochemical energy storage applications.

Hierarchical core-shell-structured bimetallic nickel-cobalt phosphide nanoarrays coated with nickel sulfide for high-performance hybrid supercapacitors

High-performance supercapacitors have attracted considerable interests due to their high-power density, fast charge/discharge process and long cycle life. However, the wide application of supercapacitors is limited by their low energy density. Herein, the hierarchical core-shell structured NiCoP@NiS nanoarrays have been successfully synthesized by using the vertically grown nickel-cobalt bimetallic phosphide (NiCoP) nanowire as the core and the nickel sulfide (NiS) by electrodeposition as the shell. As the "super channel" for electron transfer, the NiCoP core is coupled with the NiS shell to promote rapid diffusion of electrons and improve cycle stability of the electrode. Consequently, the optimized NiCoP@NiS nanoarrays display an extremely good specific capacitance (2128F g^-1 at 1 A g^-1) and a superior long cycle life (the capacitance retention of 90.36 % after 10,000 cycles). A hybrid supercapacitor (HSC) has been assembled using the NiCoP@NiS as the positive and the activated carbon (AC) as the negative, which displays a superior energy density of 30.47 Wh kg^-1 at a remarkable power energy of 800 W kg^-1. This study shows that the prepared hierarchical core-shell structured nanoarrays have great prospects as a novel electrode material in energy storage.

CuCoNi–S anchored CoMoO4/MoO3 forming core–shell structure for high-performance asymmetric supercapacitors

CoMoO4/MoO3@CuCoNi–S is prepared by hydrothermal and electrodeposition methods. It offers promising supercapacitor properties.