Construction of thickness-controllable bimetallic sulfides/reduced graphene oxide as a binder-free positive electrode for hybrid supercapacitors

Devices for electrochemical energy storage with exceptional capacitance and rate performance, outstanding energy density, simple fabrication, long-term stability, and remarkable reversibility have always been in high demand. Herein, a high-performance binder-free electrode (3D NiCuS/rGO) was fabricated as a supercapacitor by a simple electrodeposition process on a Ni foam (NF) surface. The thickness of the deposited materials on the NF surface was adjusted by applying a low cycle number of cyclic voltammetry (5 cycles) which produced a thin layer and thus enabled the easier penetration of electrolytes to promote electron and charge transfer. The NiCuS was anchored by graphene layers producing nicely integrated materials leading to a higher electroconductivity and a larger surface area electrode. The as-fabricated electrode displayed a high specific capacitance (2211.029 F g-1 at 5 mV s-1). The NiCuS/rGO/NF//active carbon device can achieve a stable voltage window of 1.5 V with a highly specific capacitance of 84.3 F g-1 at a current density of 1 A g-1. At a power density of 749 W kg-1, a satisfactory energy density of 26.3 W h kg-1 was achieved, with outstanding coulombic efficiency of 100% and an admirable life span of 96.2% after 10 000 GCD cycles suggesting the significant potential of the as-prepared materials for practical supercapacitors.

Controlling of Ni-Based Composites in Salt Melt Synthesis with High Sodium-Ion Storage Performance

Owing to its fascinating properties (such as high theoretical specific capacity and considerable conductivity), nickel sulfide (NiS) was investigated comprehensively as an anode material in sodium-ion batteries. However, they still suffered from volume expansion and sluggish kinetics, resulting in serious cycle capabilities. Herein, through controlling the kind of molten salts (Na₂SO₄, NaCl, and Na₂CO₃) in salt melt synthesis (SMS), a series of NiS with an N, S-codoped carbon layer was successfully prepared, accompanied with different morphologies and structures (earthworm-like belts and triangular and spherical particles). Tailored by the ionic strength and viscosity of molten salts, the as-prepared samples displayed different crystallization behaviors, bringing about a difference in electrochemical performance. As earthworm-like NiS@C was explored as an anode material for SIBs, an initial capacity of 712.5 mAh g^-1 at 0.5 A g^-1 could be obtained, and it still kept 527.4 mAh g^-1 after 100 cycles. Even at 2.0 A g^-1, a capacity of 508.6 mAh g^-1 could be achieved. Meanwhile, with the assistance of detailed kinetic analysis, the rapid diffusion behaviors of Na⁺ and redox reaction mechanisms of as-fabricated samples were proven for the enhanced electrochemical properties. Given this, this work is expected to provide a method for designing the morphology and structure of metal sulfides, while shedding light on the orientation of fabricating advanced electrode materials for SIBs.

Controllable synthesis of sphere-shaped interconnected interlinked binder-free nickel sulfide@nickel foam for high-performance supercapacitor applications

The fabrication of energy storage electrode materials with high specific capacitance and rapid charge–discharge capability has become an essential and major issue of concern in recent years. In the present work, sphere-shaped interconnected interlinked binder-free nickel sulfide (NiS) grown on the surface of a three-dimensional nickel foam (3DNF) was fabricated by a one-step solvothermal method under optimized synthesis conditions, including different solvents, amounts of sulfur, and experimental reaction times. The fabricated binder-free SS-NiS@3DNF-E electrodes were characterized by a range of spectroscopic and microscopic techniques and further evaluated for their comparative electrochemical supercapacitive performance in half-cell assembly cells. The optimized sphere-shaped interconnected interlinked binder-free SS-NiS@3DNF-E-3 electrode showed an outstanding specific capacitance of 694.0 F/g compared to SS-NiS@3DNF-E-1 (188.0 F/g), SS-NiS@3DNF-E-2 (470.0 F/g), and SS-NiS@3DNF-E-4 (230.0 F/g) as well as excellent cycling stability up to 88% after 6700 continuous charge–discharge cycles, with an energy density of 24.9 Wh/kg at a power density of 250.93 W/kg. The obtained results demonstrate that the interconnected interlinked binder-free NiS@nickel electrode is a potential candidate for energy storage applications.

Synthesis of P-doped NiS as an electrode material for supercapacitors with enhanced rate capability and cycling stability

Coral-like P-doped NiS nanocrystals were successfully synthesized by a two-step solvent-thermal method. The P-doped NiS electrode presented enhanced high capacitance, rate performance, and cycle life.

Significantly Enhanced Photoluminescence Performance of NixSy(NiS and Ni9S8)/ZnO Nanorods by a Hydrothermal Method

This paper reports on a near zero band gap semiconductor, Ni_xS_y, which significantly enhances the photoluminescence (PL) performance of ZnO nanorods. The structural, morphological, and optical properties of the composites were characterized by X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible spectroscopy (UV-vis), PL spectrometry, etc. The PL patterns at an excitation wavelength (λ_ex) of 325 nm revealed that the 10% Ni_xS_y/ZnO nanorod (10NZNR) composites displayed the highest emission intensity in the region of 420-630 nm. The relationship between the emission intensity of ZnO and the concentration of Ni_xS_y demonstrated that the PL intensity of NZNRs initially increased (<10%) and then declined with an increase in Ni_xS_y content (>10%). According to PL spectra at different excitation wavelengths and PL excitation (PLE) spectra, the visible emission of Ni_xS_y/ZnO nanorod (NZNR) composites can only be excited by light with energy greater than that of the band gap. Studies of the morphological structures and PL behaviors of NZNR composites have illustrated that Ni_xS_y considerably enhances the visible emission of ZnO by regulating its morphology and structure. An appropriate mechanism by which Ni_xS_y enhances the PL performance of ZnO has been proposed.

Sulphur Source-Inspired Self-Grown 3D Ni xS y Nanostructures and Their Electrochemical Supercapacitors

Sulphur source-inspired self-grown polycrystalline and mesoporous nickel sulfide (Ni _xS _y) superstructures with vertically aligned nanomorphologies viz. rods, flakes, buds, and petals, synthesized at elevated temperatures and moderate pressures by a facile one-pot hydrothermal method on a three-dimensional Ni foam demonstrate remarkable areal specific capacitances of 7152, 4835, and 2160 F cm^-2 at current densities of 1, 2, and 5 mA cm^-2, respectively, with a cycling stability of 94% for a battery-type electrochemical supercapacitor when used as an electrode material in a supercapacitor. The Ni _xS _y//Bi₂O₃ asymmetric supercapacitor assembly exhibits an energy density of 41 W h·kg^-1 at a power density of 1399 W kg^-1 for 1 A g^-1 and was used in a three-cell series combination to operate a "GFHIM" display panel (our research institute name, Global Frontier R & D Center for Hybrid Interface Materials) composed of nearly 50 differently colored light-emitting diodes with high intensity in 1 M KOH water-alkali electrolyte. The electrochemical supercapacitor results obtained for the Ni _xS _y superstructures because of a combination of catalytically active amorphous and high mobility polycrystalline are highly comparable to those reported previously for salt-mediated and self-grown Ni _xS _y structures and morphologies.

A cabbage leaf like nanostructure of a NiS@ZnS composite on Ni foam with excellent electrochemical performance for supercapacitors

In the present study, a NiS@ZnS composite nanostructure was synthesized on a nickel foam substrate by a facile chemical bath deposition (CBD) method.

Development of Novel and Ultra-High-Performance Supercapacitor Based on a Four Layered Unique Structure

This paper presents an electrode with a core/shell geometry and a unique four-layered porous wrinkled surface for pseudocapacitive supercapacitor applications. To design the electrode, Ni foam was used as a substrate, where the harmonious features of four constituents, ZnO (Z), NiS (N), PEDOT:PSS (P), and MnO2 (M) improved the supercapacitor electrochemical performance by mitigating the drawbacks of each other component. Cyclic voltammetry and galvanostatic charge discharge measurements confirmed that the ZNPM hybrid electrode exhibited excellent capacitive properties in 2 M KOH compared to the ZNP, ZN, and solely Z electrodes. The ZNPM electrode showed superior electrochemical capacitive performance and improved electrical conductivity with a high specific capacitance of 2072.52 F g−1 at 5 mA, and a high energy density of 31 Wh kg−1 at a power density of 107 W kg−1. Overall, ZNPM is a promising combination electrode material that can be used in supercapacitors and other electrochemical energy conversion/storage devices.