Ultra-thin NiS nanosheets as advanced electrode for high energy density supercapacitors

Hydrothermal Synthesis of β-NiS Nanoparticles and Their Applications in High-Performance Hybrid Supercapacitors

In this work, β-NiS nanoparticles (NPs) were efficiently prepared by a straightforward hydrothermal process. The difference in morphology between these NiS NPs was produced by adding different amounts of thiourea, and the corresponding products were denoted as NiS-15 and NiS-5. Through electrochemical tests, the specific capacity (Cs) of NiS-15 was determined to be 638.34 C g-1 at 1 A g-1, compared to 558.17 C g-1 for NiS-5. To explore the practical application potential of such β-NiS NPs in supercapacitors, a hybrid supercapacitor (HSC) device was assembled with activated carbon (AC) as an anode. Benefitting from the high capacity of the NiS cathode and the large voltage window of the device, the NiS-15//AC HSC showed a high energy density (Ed) of 43.57 W h kg-1 at 936.92 W kg-1, and the NiS-5//AC HSC provided an inferior Ed of 37.89 W h kg-1 at 954.79 W kg-1. Both HSCs showed excellent cycling performance over 6000 cycles at 10 A g-1. The experimental findings suggest that both NiS-15 and NiS-5 in this study can serve as potential cathodes for high-performance supercapacitors. This current synthesis method is simple and can be extended to the preparation of other transition metal sulfide (TMS)-based electrode materials with exceptional electrochemical properties.

Nanoarchitectonics of Three-Dimensional Carbon Nanofiber-Supported Hollow Copper Sulfide Spheres for Asymmetric Supercapacitor Applications

Three-dimensional carbon nanofiber (3D-CNF)-supported hollow copper sulfide (HCuS) spheres were synthesized by the facile hydrothermal method. The morphology of the as-synthesized HCuS@3D-CNF composite clearly revealed that the 3D-CNFs act as a basement for HCuS spheres. The electrochemical performance of as-synthesized HCuS@3D-CNFs was evaluated by cyclic voltammetry (CV) tests, gravimetric charge-discharge (GCD) tests, and Nyquist plots. The obtained results revealed that the HCuS@3D-CNFs exhibited greater areal capacitance (4.6 F/cm²) compared to bare HCuS (0.64 F/cm²) at a current density of 2 mA/cm². Furthermore, HCuS@3D-CNFs retained excellent cyclic stability of 83.2% after 5000 cycles. The assembled asymmetric device (HCuS@3D-CNFs//BAC) exhibits an energy density of 0.15 mWh/cm² with a working potential window of 1.5 V in KOH electrolyte. The obtained results demonstrate that HZnS@3D-CNF nanoarchitectonics is a potential electrode material for supercapacitor applications.

Review of NiS-Based Electrode Nanomaterials for Supercapacitors

As a new type of energy storage device, supercapacitors have the advantages of high-power densities, high safety factors, and low maintenance costs, so they have attracted widespread attention among researchers. However, a major problem with supercapacitors is that their energy densities are not high enough, which limits their application. Therefore, it is crucial to expand the application scenarios of supercapacitors to increase their energy density as much as possible without diminishing their advantages. The classification and working principles of supercapacitors are introduced in this paper. The electrochemical properties of pure NiS materials, NiS composites with carbon materials, NiS composites with sulfide materials, and NiS composites with transition metal oxides for supercapacitors are summarized. This paper may assist in the design of new electrode materials for NiS-based supercapacitors.

Hierarchical crumpled NiMn2O4@MXene composites for high rate ion transport electrochemical supercapacitors

MXenes have received great attention due to their excellent features such as metal-like electronic conductivity, hydrophilic surface groups, and high volumetric capacitance. However, many performances of MXenes are still unsatisfactory due to their low energy density and easy horizontal stacking. In this work, an NiMn2O4@MXene composite with a crumpled surface was fabricated by a hydrothermal method and a developed dip-coating method. The maximum specific capacitance of the electrode is about 1.52 times that of NiMn2O4. Besides, it delivers a retention rate of 93.3% after 4000 cycles due to the increased transport of ions and electrons by the crumpled surface. An asymmetrical device based on the crumpled NiMn2O4@MXene composite and AC was also assembled, which shows an ultra-high energy density. This work provides an effective strategy to solve the vertical stacking problem of MXenes, which can open new avenues for large-scale applications of MXenes in energy storage.