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Cobalt-manganese bimetallic oxide MnCo2O4 has potential application value in the research of cathode materials for supercapacitors. The structure of the MnCo2O4 nanomaterial directly affects its electrochemical performance. A series of MnCo2O4 electrode materials with different sintering temperatures were obtained by hydrothermal synthesis of a cobalt-manganese precursor. The relationship between the microstructure and electrochemical properties of the samples was investigated. The sample sintered at 700°C had the best electrochemical performance, and the specific capacity of the sample reached 2065 F g−1 at 1 A g−1. The assembled asymmetric supercapacitor MCO-700//AC had a capacity retention rate of 67% after 10,000 cycles at 20 A g−1. The stable structure and excellent electrochemical performance of MnCo2O4 material were obtained by controlling the sintering temperature, which provides a reference for developing cobalt-manganese-based capacitor materials. [ABSTRACT FROM AUTHOR]

To improve the electrochemical performance of the supercapacitor, three electrode nanocomposites, NiO, NiS and NiCo2S4, have been obtained by simple hydrothermal process and high temperature pyrolysis, and further, the impact of electrolytes of different concentrations on electrochemical performance of supercapacitor has been researched. During the research processing, synergistic effect of Ni, Co and S is considered to enhance the electrical conductivity, and promote electron transfer, ion diffusion and structural stability. The experiment results show that bimetallic sulfides display high electrical conductivity, shorter ion diffusion channels, and faster electron and ion transport rate with the feature of topping electrochemical properties of specific capacity, excellent cycling stability and high rate capability, and besides show that it can improve the electrochemical performance of the material by increasing the concentration of electrolyte. The transition-metal sulfides provide a new promising pathway for the expansion of high-performance electrode materials for supercapacitors. In this paper, the three-dimensional structure of NiCo2S4 nanomaterial is prepared by two-step hydrothermal method and applied to the electrode material of supercapacitor. First, the microstructure of the material is analyzed through physical characterization, and then its electrochemical performance was tested in the three-electrode system. [ABSTRACT FROM AUTHOR]

Co‐doped Mo1‐xCoxS2(x=0, 0.1, 0.3, 0.5) nanoparticles with varying amounts of Co were compounded by hydrothermal channel. The microstructures of the samples were characterized. All the samples showed hexagonal structure, good crystallization, flower shape microspheres and agglomeration to a certain extent. Furthermore, the influence of Co doping on the electrochemical properties was evaluated by cyclic voltammetry (CV), galvanostatic charge‐discharge (GCD), cycle stability and electrochemical impedance spectra (EIS). CV curves present quasi‐triangular shapes with good symmetry, doped Mo1‐xCoxS2 nanoparticles exhibit better specific capacitance and excellent cyclic stability than that of MoS2 samples. The capacity ratios of MCS‐3 electrodes maintains 96 % of its premier capacitance after 3000 cycles. The remarkable electrochemical properties embodied in CV proof were proved via the GCD measurements. Nyquist spectra of doped Mo1‐xCoxS2 electrodes reveal lower resistance and perfect conductivity. This work reveals that Co doping can further effectively the electrochemical properties of MoS2 nanomaterials. [ABSTRACT FROM AUTHOR]

In recent years, the development of MoS2 as supercapacitor electrode material has been widely reported, and most of them adopt a single method to improve the electrochemical performance of MoS2. Pure MoS2 has poor intrinsic conductivity and easy aggregation, which impedes its electrochemical performance and greatly limits its practical application. In this paper, Co-doped MoS2 was used as the substrate to compound with g-C3N4 to improve the electrochemical performance of MoS2. Mo0.7Co0.3S2/g-C3N4 nanocomposites with different mass ratio were successfully synthesized via solvothermal method. The effects of different ratios on the microstructure and electrochemical properties of samples were studied by a series of tests. The experimental results indicate that Mo0.7Co0.3S2/g-C3N4 nanocomposites are hexagonal structure with good crystallization, the morphologies are mainly nanosheet structure, and Mo0.7Co0.3S2 nanoparticles are uniformly embedded on the surface of g-C3N4 nanosheets. Mo0.7Co0.3S2/g-C3N4 nanocomposites show pseudocapacitance behavior and excellent electrochemical performance, in particular, MCS/CN-2 electrodes (mass ratio of Mo0.7Co0.3S2:g-C3N4 is 9:1) exhibit the best electrochemical performance. This work improves the performance of MoS2 as electrode material of supercapacitor material through doping modification and composite of carbon material and provides reference value for subsequent research. [ABSTRACT FROM AUTHOR]

In this paper, the Ni 1. 5 Co 1. 5 S4@CNTs nanocomposites containing different carbon nanotubes (CNT) content were prepared by a one-step hydrothermal method. More hydroxyl and carboxyl groups were introduced on the surface of CNTs by acidizing treatment to increase the dispersion of CNTs. The acid-treated CNTs can more fully compound with Ni 1. 5 Co 1. 5 S4 nanoparticles to form heterostructure. When the CNTs content is 10 wt.%, the Ni 1. 5 Co 1. 5 S4@CNTs-10 nanocomposite exhibits the highest specific capacity of 210 mAh g − 1 in KOH aqueous electrolytes at current density of 1 A g − 1 . The superior performances of the Ni 1. 5 Co 1. 5 S4@CNTs-10 nanocomposite are attributed to the effective synergic effects of the high specific capacity of Ni 1. 5 Co 1. 5 S4 and the excellent conductivity of CNTs. An asymmetric supercapacitor (ASC) was assembled based on Ni 1. 5 Co 1. 5 S4@CNTs-10 positive electrode and activated carbon (AC) negative electrode, which delivers a high energy density of 61.2 Wh kg − 1 at a power density of 800 W kg − 1 , and maintains 34.8 Wh kg − 1 at a power density of 16079 W kg − 1 . Also, the ASC device shows an excellent cycling stability with 91.49% capacity retention and above 94% Columbic efficiency after 10 000 cycles at 10 A g − 1 . This aqueous asymmetric Ni 1. 5 Co 1. 5 S4@CNTs//AC supercapacitor is promising for practical applications due to its advantages such as high energy density, power delivery and cycling stability. The Ni1.5Co1.5S4@CNTs nanocomposites have been prepared by a hydrothermal route. The Ni1.5Co1.5S4@CNTs nanocomposite with 10 wt.% CNTs shows a high specific capacity owing to maximizing synergic effects of high specific capacity of the Ni-Co metal sulfide and excellent conductivity of CNTs. A supercapacitor based on the Ni1.5Co1.5S4@CNTs nanocomposite is promising for practical applications due to its high energy density, high power delivery and low cost. [ABSTRACT FROM AUTHOR]

At present, the specific capacity and cyclic stability of single cobalt manganese oxide are still insufficient to meet the application requirements. In this work, (Co,Mn)(Co,Mn) 2 O 4 /g-C 3 N 4 electrode materials with different mass ratios were synthesized by adjusting the composite ratio of g-C 3 N 4 and (Co,Mn)(Co,Mn) 2 O 4. The results of the three-electrode test system show that the electrochemical performance of the composite sample is improved compared with that of pure (Co,Mn)(Co,Mn) 2 O 4. When the mass ratio of g-C 3 N 4 to (Co,Mn)(Co,Mn) 2 O 4 is 1:9, the electrochemical performance is the best. This is because layered g-C 3 N 4 can provide more active sites for electrochemical reactions and increase the wettability of the material, thus improving the electrochemical reaction process. The power density of the assembled asymmetric supercapacitor CMO/GCN-2//AC can reach 16800 ​W ​kg−1 at an energy density of 14 ​Wh kg−1. Schematic representation of the synthesized (Co,Mn)(Co,Mn) 2 O 4 /g-C 3 N 4 structure. The granular form represents (Co,Mn)(Co,Mn) 2 O 4 , and the coloured layered structure is g-C 3 N 4. This structure improves the electrochemical reaction kinetics of the material. [Display omitted] • The specific capacity and cyclic stability of single cobalt-manganese oxides are relatively poor. The presence of lone pair electrons in g-C 3 N 4 nitrogen atoms induces greater polarity in the molecule, enhancing the wettability and carrier mobility of the material. In this paper, (Co,Mn)(Co,Mn) 2 O 4 /g-C 3 N 4 electrode material with different composite ratio was prepared. • The results of the three-electrode test system show that the electrochemical performance of the composite sample is improved compared with that of pure (Co,Mn)(Co,Mn) 2 O 4. When the mass ratio of g-C 3 N 4 to (Co,Mn)(Co,Mn) 2 O 4 is 1:9, the composite sample has the best electrochemical performance. • The power density of the assembled asymmetric supercapacitor CMO/GCN-2//AC can reach 16800 ​W ​kg−1 at energy density of 14 ​Wh kg−1. [ABSTRACT FROM AUTHOR]

The phase-transition engineering has shown great potential in designing high-performance energy storage and catalytic materials. Herein, we report the phase transition and selenium vacancy induced by the trace boron doping into CoSe 2 , realizing an enhancement of the performance of supercapacitor. The trace amounts of boron doping (∼ 0.07 wt%) induce the phase-transition from cubic to orthorhombic structures and trigger selenium vacancies in orthorhombic cobalt diselenide (o-CoSe 2). The doped defective cobalt diselenide (o-CoSe 2−x /B) exhibits a high specific capacity of 376.3 mA h g−1 at a current density of 1 A g−1, which is much larger than that of the undoped cubic cobalt diselenide (211.3 mA h g−1) and annealed cubic cobalt diselenide (208.3 mA h g−1). A hybrid supercapacitor assembled using o-CoSe 2−x /B and activated carbon delivers a high energy density of 102.5 W h kg−1 at a power density of 850.4 W kg−1 and maintains an energy density of 34.0 W h kg−1 at 16,767.1 W kg−1. In addition, the device possesses an excellent cycling stability that remains 83.5 % of the initial capacitance after 25,000 cycles at a current density of 10 A g−1. These results demonstrate that the boron is a new efficient dopant that can dramatically improve the supercapacitor performance of CoSe 2 through the structural phase transition and defect engineering. [Display omitted] • Trace amounts of boron induces phase-transition from c-CoSe 2 to o-CoSe 2. • Se vacancies defects arise with the help of boron doping engineering. • The o-CoSe 2−x /B shows the enhanced performance as electrode for supercapacitor. • Providing an efficient dopant for design of CoSe 2 based energy storage materials. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the MnO 2 /three-dimensional carbon nanotubes-graphene nanocomposite was synthesized on Cu foil substrate by chemical vapor deposition and subsequent thermal decomposition of manganese acetyllacetonate precursors. The nanocomposite material was directly used as a binder-free electrode to investigate the supercapacitive performance. The results indicate that the appropriate defects and MnO 2 nanoparticles are introduced simultaneously into the carbon nanotubes-graphene architecture in one-step. The specific capacitance of MnO 2 /three-dimensional carbon nanotubes-graphene/Cu electrode is up to 365 F g−1 at a current density of 1 A g−1 in 1.0 M Na 2 SO 4 solution, which is 9 times higher than that of electrode without MnO 2 modification. After 1000 cycles at 1 A g−1, the capacity retention is still maintained at 97.0%, suggesting potential applications in high-performance energy storage devices. The excellent electrochemical performances of nanocomposite electrode can be attributed to the significantly synergistic effects between the lasting electronic conductivity of three-dimensional carbon nanotubes-graphene/Cu with the appropriate defects and the pseudocapacitance of the MnO 2 nanoparticles. Graphical abstract Image 1 Highlights • MnO 2 /3D CNTs-G/Cu was fabricated as a binder-free electrode using a facile method. •Defects and α-MnO 2 was introduced simultaneously into the 3D CNTs-G/Cu in one-step. •The specific capacitance of MnO 2 /3D CNTs-G/Cu reached 365 F g−1 at 1 A g−1 current. •Synergistic effects of 3D CNTs-G/Cu lasting conductivity and MnO 2 pseudocapacitance. [ABSTRACT FROM AUTHOR]

• Utilizing the well-designed Ni 2 CoS 4 @ZIF-67 precursor as self-sacrificing templates. • Constructing the porous α-Ni(Co)S@NiCoO 2 composites with core–shell like structure. • Novel combination of Ni-Co-S and Ni-Co-O shows outstanding capacitive performance. As inspired by the surging demand for high performance energy storage systems, researchers have been designing and exploring advanced electrode materials exhibiting higher energy and power densities. In this study, a novel combination of nickel-cobalt sulfide and oxide was reported for high performance supercapacitors. The porous α-Ni(Co)S@NiCoO 2 composites with core–shell structure were derived from the well-designed precursor with Ni 2 CoS 4 and ZIF-67 serving as the self-sacrificing templates through a two-step calcination process at elevated temperatures. Such a heterostructure exhibited an ultra-high specific capacity of 502.4 mA h g–1 at a current density of 1 A g–1, which was attributed to the unique porous core–shell structure and the ingenious combination of bimetallic sulfide and oxide. Furthermore, a hybrid supercapacitor based on the α-Ni(Co)S@NiCoO 2 composite and commercial activated carbon achieved a high energy density of 82.4 Wh kg–1 at a power density of 847.5 W kg–1. The prominent electrochemical performance exhibited by the α-Ni(Co)S@NiCoO 2 heterostructure in this study was demonstrated to be promising to practically serve as advanced electrode materials in supercapacitors. [ABSTRACT FROM AUTHOR]

• The CNTs/NiCo 2 S 4 hybrids with three kinds of interfaces were designed and prepared. • Supercapacitive properties of CNTs/NiCo 2 S 4 were improved by interface regulation. • An aqueous asymmetric supercapacitor was successfully assembled and evaluated. • An CNT:Ni@NiCo 2 S 4 //AC device showed excellent electrochemical energy storage. Integrating metal sulfides with carbon materials is considered as one of effective approaches to meet the demand of high-performance electrochemical energy storage materials. In this paper, we emphasize the critical role of interface between NiCo 2 S 4 and CNTs for supercapacitive performance of the hybrid structures. The CNTs/NiCo 2 S 4 nanocomposites with three kinds of interfaces are prepared using a one-step hydrothermal method by adding the pristine CNTs, surface-oxidized CNTs and nickel-coated CNTs, respectively. Benefiting from the unique nickel interface structure that adequately realizes the effective utilization of the conductive CNTs owing to the homogeneous dispersion of CNTs throughout the matrix as well as the strong interface adhesion by a bridging role, the CNTs:Ni@NiCo 2 S 4 nanocomposite exhibits a high specific capacity of 224.0 mAh g−1 at a current density of 1 A g−1. An asymmetric supercapacitor assembled by the CNTs:Ni@NiCo 2 S 4 nanocomposite and activated carbon as positive electrode and negative electrode, respectively, exhibits a high energy density of 60.7 Wh kg−1 at a power density of 800 W kg−1 and an excellent cycling stability of 88% capacitance retention after 10,000 cycles at 10 A g−1. This work described herein provides a new strategy for development of high-performance energy storage materials. [ABSTRACT FROM AUTHOR]