As a promising cathode material for aqueous zinc-ion batteries, 1T-MoS2 has been extensively investigated because of its facile two-dimensional ion-diffusion channels and high electrical conductivity. However, the limited number of available Zn storage sites, i.e., limited capacity, hinders its application because the inserted Zn2+, which form strong electrostatic interactions with 1T-MoS2, preventing subsequent Zn2+ insertion. Currently, the approach of enlarging the interlayer distance to reduce electrostatic interactions has been commonly used to enhance the capacity and reduce Zn2+ migration barriers. However, an enlarged interlayer spacing can weaken the van der Waals force between 1T-MoS2 monolayers, easily disrupting the structural stability. Herein, to address this issue, an effective strategy based on Fe doping is proposed for 1T-MoS2 (Fe-1T-MoS2). The theoretical calculations reveal that Fe doping can simultaneously moderate the rate of decrease in the adsorption energy after gradually increasing the number of stored atoms, and enhance the electron delocalization on metal-O bonds. Therefore, the experiment results show that Fe doping can simultaneously activate more Zn storage sites, thus enhancing the capacity, and stabilize the structural stability for improved cycling performance. Consequently, Fe-1T-MoS2 exhibits a larger capacity (189 mAh·g−1 at 0.1 A·g−1) and superior cycling stability (78

delta-MnO2 was proposed as a promising cathode material for aqueous Zn-ion batteries. Nonetheless, its potential application has been impeded by its unstable crystal structure and sluggish reaction kinetics with Zn ions. Herein, we utilized Cr to modify delta-MnO2 by a simple hydrothermal method to develop cathode materials for aqueous Zn-ion batteries with better stability and electron transport properties. The introduction of Cr enhanced the specific capacity and cycling stability of delta-MnO2, in particular, the 3% Cr doped delta-MnO2 electrode exhibited a large specific capacity of 229.2 mAhg(-1) at 0.1 Ag(-1) and an excellent capacitance retention of 86.0% after performing 300 cycles. The density functional theory (DFT) calculations indicate that the introduction of Cr decreases the band gap of MnO2 and enhances electron migration in the electrode material. Meanwhile, the introduction of Cr substantially improved the Zn ion adsorption and enhanced the binding energy of delta-MnO2, indicating that the addition of Cr promoted the interaction between the Cr doping delta-MnO2 (Cr-MnO2) electrode materials with Zn ions, while making the structure of the electrode materials more stable. As a result, this suppresses the Jahn-Teller distortion and reduces the solvation and phase transition of Mn.

In this study, copper oxide (CuO) nanosheet arrays arc synthesized on a copper substrate by using the water bath mcthod. The CuO nanosheet arrays formed after a 10-min reaetion time exhibit the highest initial discharge specific capacity of 629.1 mA.h-g(-1) and good cycle properties (79. 6 %) retention after 100 cycles). When compared with the traditional bulk copper oxide anode materials, the CuO nanosheet array structure used as the negative electrode material for lithium ion batteries effectively solves the volume expansion during charging. Furthermore, it reduces the diffusion distance of the lithium ion in the CuO crystal, improving the specific capacity and performance of CuO used as the negative electrode materials.

Co/CoO core-shell nanostructure on the 3D nickel foam has been synthesized by a hydrothermal method following by annealing the precursor in hydrogen atmosphere and air respectively. Different shell thicknesses of the CoO are designed and controlled by annealing the nanostructured Co in the air at 50 degrees C, 100 degrees C, 150 degrees C, 200 degrees C for 2 h, which were characterized by X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectronspectroscopy (XPS). As a result, Co/CoO core-shell nanostructure annealed at 150 degrees C achieved the best electrochemical performance (ultrahigh areal capacitance of 6.08 F cm(-2)), which was superior to those treated in other temperatures. An asymmetric supercapacitor device was assembled by using the Co/CoO core-shell nanostructure (positive electrode) and the active carbon (negative electrode), which can deliver a working voltage of 1.5 V, and display a high energy density of 0.51 mWh cm(-2) at a power density of 2.03 mW cm(-2). The results show that the Co/CoO core-shell nanostructure has potential application prospect in the pseudocapacitor. (C) 2017 Elsevier B.V. All rights reserved.

Hydrous NiMoO4 nanoflake arrays on Ni foam show superior cycle ability and specific capacitance.

A three dimensional (3D) porous framework-like N-doped carbon (PFNC)-with a high specific surface area was successfully fabricated through ammonia doping and graphitization based on pomelo peel. The obtained PFNC exhibits an enhanced specific capacitance (260 F g(-1) at 1 A g(-1)) and superior cycling performance (capacitance retention of 84.2% after 10000 cycles at 10 A g(-1)) on account of numerous voids and pores which supply sufficient pathways for ion diffusion during cycling. Furthermore, a fabricated asymmetric PFNC//PFN device based on PFNC and porous flake-like NiO (PFN) arrays achieves a specific capacitance of 88.8 F g(-1) at 0.4 A g(-1) and an energy density of 27.75 Wh kg(-1) at a power density of 300 W kg(-1) and still retains 44 F g(-1) at 10 A g(-1) and 13.75 Wh kg(-1) at power density of 7500 W kg(-1). It is important that the device is able to supply two light-emitting diodes for 25 min, which demonstrates great application potential.

A high-performance supercapacitor electrode is designed and fabricated with the 3D interconnected continuous nanoporous Co/CoO core-shell hybrid nanostructure grown on nickel foam. The Co/CoO core-shell hybrid nanostructures are obtained via a hydrothermal method, followed by high-temperature annealing in hydrogen atmosphere, and finally placed in air at 50 °C for 1 h. The Co/CoO core-shell nanostructure assembled by a conductive metal-core and a CoO shell, brings low resistance, high specific capacitance of 5.632 F cm-2 and good capability stability (81.5% capacitance retention after 6000 cycles). An asymmetric supercapacitor device built by the Co/CoO (positive electrode) and activated carbon (negative electrode) can deliver a working voltage of 1.7 V and display a high energy density of 0.002 67 Wh cm-2 at a power density of 0.001 62 W cm-2, which is far superior to that of a supercapacitor at a similar power density.

A novel chemical successive ionic layer adsorption and reaction (SILAR) method has been used for the synthesis of hierarchical nanostructured material by growing Cu2O-Mn3O4 nanoflakes onto TiO2 crumpled micro-nano spheres, which were prepared by hydrothermal method on Ti foil substrate. The nanocomposites of TiO2/Cu2O-Mn3O4 are strategically combined into a single entity to synergize and construct a high electrochemical performance of pseudocapacitor electrode. Specific capacitance of the ternary composite electrode achieves as high as 259 F g(-1) at a current density of 3 A g(-1), when cycling performance (no capacity loss over 5000 cycles) is much better than that of TiO2/Mn3O4, TiO2/Cu2O and individual component Mn3O4 electrodes. (C) 2016 Elsevier B.V. All rights reserved.

A sandwich-structured porous supercapacitor electrode layered by MnO2/Polyaniline/MnO2 (MPM) was constructed by electrochemical deposition and in situ polymerization method. As a supercapacitor electrode, it had uniform mesoporous structure and a fast electron transport high-way due to the electrochemical deposition method and the middle thin layer of conductive polyaniline which could dramatically enhance the conductivity of MnO2. In three-electrode system, this sandwich-structured MPM electrode has superior capacitive performance to electrode which consists of only two layers of MnO2 (MM). (C) 2015 Elsevier B.V. All rights reserved.

NiCo2S4 and carbon-NiCo2S4 hetero-structured nanosheet arrays have been firstly synthesized on nickel foams in a facile hydrothermal and CVD method. The products NiCo2S4 and carbon-NiCo2S4 are obtained in Na2S aqueous solution in a hydrothermal reaction from precursor of NiCox(OH)y and carbon-NiCo2O4 through anion exchange respectively, which are characterized by XRD, TEM, Raman analysis. The obtained binary metal sulphide NiCo2S4 nanosheet delivers better electrochemical activity and higher mass loading compared with NiCo2O4. In addition, carbon introduced enhances the capacitive behaviours and cycle performance for enhanced electric conductivity and stable architecture. The integrated carbon-NiCo2S4 electrode exhibits high areal capacitance of 8.33Fcm−2 and ultrahigh specific capacitance of 1893.2Fg−1 with a potential window of 0.8V and high mass loading of 4.4mgcm−2 and good cycle performance in a three-electrode system. The asymmetric supercapacitor is further assembled using carbon-NiCo2S4 as the positive electrode and activated carbon as the negative electrode. The integrated asymmetric supercapacitor demonstrates a high energy density of 68.82Whkg−1 at a power density of 47.83Wkg−1, which confirms its practical applicability.

We report a facile, rapid and low-cost two step approach to synthesize hierarchical CuO@MnO2 core-shell nanosheet arrays directly on Cu foil substrate. The as prepared CuO@MnO2 arrays can be directly used as integrated electrodes. Furthermore, the CuO@MnO2 nanosheet arrays were assembled with the commercial Li Ion Battery Cathode (LiCoO2) as a full cell, which exhibited high capacity and good cycle stability (120 mA h g(-1) after 100 cycles at a rate of 150 mA g(-1)) and an excellent rate performance (a stable capacity of about 127 mA h g(-1) after 100 cycles of variable charging rate). The excellent performance of the CuO@MnO2 hybrids comes from their intelligent integration of the two compatible components into unique hierarchical architectures with a high specific capacity. Primary single-crystalline CuO nanosheet arrays directly grown on Cu substrates allow for efficient electrical and ionic transport. The secondary MnO2 shell provide enhanced surface area and high theoretical Li+ storage capacity, and can also serve as volume spacers between neighboring CuO nanosheet arrays to maintain electrolyte penetration as well as reduce the aggregation during Li+ intercalation, thus leading to improved electrochemical energy storage performance. (C) 2015 Elsevier B.V. All rights reserved.

CuO nanoarrays (CNAs) and Fe-incorporated CuO nanoarrays (FCNAs) were fabricated by hydrothermal method. Addition of Fe salt to the reaction mixture allowed the introduction of iron oxide onto the CNAs surface, which was characterized by XPS and HRTEM. Introducing Fe ion into reaction precursor significantly affected not only the morphologies of as-prepared products but also their electrochemical performance as anode for lithium ion full battery. The FCNAs electrodes showed higher specific capacity and better capacity retention at different current densities than that of CNAs. (C) 2015 Elsevier B.V. All rights reserved.

Manganese dioxide (MnO2) and CuBi2O4-doped MnO2 thin films with different nanostructures were deposited on indium tin oxide (ITO) glass and Ti foil substrates by using a chemical bath deposition (CBD) technique. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron microscopy (XPS). The effects of doping and substrates on electrochemical properties of MnO2 and CuBi2O4-doped MnO2 thin films on ITO glass and Ti foil were investigated. Capacitive properties of MnO2 and CuBi2O4-doped MnO2 thin films electrodes were studied using cyclic voltammetry and electrochemical impedance spectroscopy in a three-electrode experimental setup using 0.1M Na2SO4 aqueous solution as electrolyte. Specific capacitance, obtained from electrochemical measurement for the CuBi2O4-doped MnO2, exhibited a higher value of 338Fg−1 compared to the MnO2 exhibiting value of 135Fg−1. In addition, CuBi2O4-doped MnO2 thin films on an ITO electrode had a better and satisfactory specific capacitance value, and exhibited more excellent electrochemical stability and reversibility than Ti foil substrates.

A novel carbon-CoO-NiO-NiCo2O4 integrated electrode has been designed by reducing the hetero-structured NiCo2O4 nanosheet array with C2H2 on the nickel foam at a low temperature of 350 °C. The topotactical transformation from NiCo2O4 to the integrated electrode has been first conceived and investigated. Such unique nanoarchitectures exhibit excellent electrochemical performance with ultrahigh capacitance and desirable cycle life at high rates.

Highly conductive carbon–CoO nanowire array electrodes on 3D nickel foam were designed with ultrahigh specific capacitance (3282.2 F g−1), approaching the CoO theoretical value. Assembled into an asymmetric supercapacitor, the energy density is ∼58.9 W h kg−1, a record among Co-based supercapacitors.

One-dimensional CuO nanoribbons and three-dimensional CuO nanoflowers were synthesized via a facile, rapid, low-temperature, one-pot water bath method, in which the synthesis was performed in Cu(CH3COO)2/NaOH and aqueous/ethanol systems at 70 °C for 15 min. Control over the shape and dimensionality of the well-defined CuO single crystals was achieved simply by varying the order of addition of the reactive materials. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction were used to characterize the products. The formation mechanism in the in situ, rapid reaction was investigated. In Brunauer-Emmett-Teller and thermogravimetry measurements, the nanoribbons exhibited a higher specific surface area and higher adsorption capabilities than the nanoflowers. Using cyclic voltammetry, chronopotentiometry and EIS measurement for supercapacitance, it was shown that the nanoflower electrodes had better performance than the nanoribbon electrodes, however, the nanoribbon/C electrodes had better performance than the nanoflower/C electrodes at lower current density, but were worse at higher current density.