Carbon Nanotubes@Nickel Cobalt Sulfide Nanosheets for High‐Performance Supercapacitors

Overview of recent developments in carbon-based nanocomposites for supercapacitor applications

Energy storage devices are recognized as environmentally friendly technologies. Supercapacitors, known for their high cycle stability, have been proposed as potential alternatives to fossil fuels. Recent studies have focused on selecting suitable electrode materials to achieve energy storage systems with high stability, high specific capacity, and biocompatibility. In particular, carbon-based electrode materials, such as graphene oxide, activated carbon, carbon nanotubes, and carbon-based quantum dots, have attracted considerable attention due to their intrinsic properties, such as high conductivity and stability. However, carbon materials alone exhibit limitations, such as low energy density and low specific capacitance. To address this limitation, the synergistic effect of carbon materials has been combined with other electroactive materials to develop electrode materials with enhanced supercapacitor properties. The present study also investigates the supercapacitor performance of carbon-based nanocomposites. It examines the effect of each carbon material (AC, CNT, GO, rGO) on improving the performance of other electroactive materials, including metal oxides, metal sulfides, MXenes, MOFs, and conductive polymers. This study provides valuable insights for further studies on carbon-based electrode materials for supercapacitor applications.

Engineering NiCo2S4 nanoparticles anchored on carbon nanotubes as superior energy-storage materials for supercapacitors

Fabricating high-capacity electrode materials toward supercapacitors has attracted increasing attention. Here we report a three-dimensional CNTs/NiCo2S4 nanocomposite material synthesized successfully by a facile one-step hydrothermal technique. As expected, a CNTs/NiCo2S4 electrode shows remarkable capacitive properties with a high specific capacitance of 890 C g-1 at 1 A g-1. It also demonstrates excellent cycle stability with an 83.5% capacitance retention rate after 5000 cycles at 10 A g-1. Importantly, when assembled into a asymmetric supercapacitor, it exhibits a high energy density (43.3 W h kg-1) and power density (800 W kg-1). The exceptional electrochemical capacity is attributed to the structural features, refined grains, and enhanced conductivity. The above results indicate that CNTs/NiCo2S4 composite electrode materials have great potential application in energy-storage devices.

Tailoring the Hollow Structure within CoSn(OH)6 Nanocubes for Advanced Supercapacitors

The enhanced application performance of hollow-structured materials is attributed to their large surface area with more active sites. In this work, the hollow CoSn(OH)₆ nanocubes with increased surface area and mesopores were derived from dense CoSn(OH)₆ nanocube precursors by alkaline etching. As a result, the hollow CoSn(OH)₆ nanocubes-based cathode electrode exhibited a higher area-specific capacitance of 85.56 µF cm^-2 at 0.5 mA cm^-2 and a mass-specific capacitance of 5.35 mF g^-1 at 0.5 mA cm^-2, which was more extensive than that of the dense precursor. Meanwhile, the current density was increased 4-fold with good rate capability for hollow CoSn(OH)₆ nanocubes.

NiCo2S4nanosheets decorated on nitrogen-doped hollow carbon nanospheres as advanced electrodes for high-performance asymmetric supercapacitors

Taking advantage of both Faradaic and carbonaceous materials is an efficient way to synthesize composite electrodes with enhanced performance for supercapacitors. In this study, NiCo₂S₄nanoflakes were grown on the surface of nitrogen-doped hollow carbon nanospheres (NHCSs), forming a NiCo₂S₄/NHCS composite with a core-shell structure. This three-dimensionally confined growth of NiCo₂S₄can effectively inhibit its aggregation and facilitate mass transport and charge transfer. Accordingly, the NiCo₂S₄/NHCS composite exhibited high cycling stability with only 9.2% capacitance fading after 10 000 cycles, outstanding specific capacitance of 902 F g^-1at 1 A g^-1, and it retained 90.6% of the capacitance at 20 A g^-1. Moreover, an asymmetric supercapacitor composed of NiCo₂S₄/NHCS and activated carbon electrodes delivered remarkable energy density (31.25 Wh kg^-1at 750 W kg^-1), excellent power density (15003 W kg^-1at 21.88 Wh kg^-1), and satisfactory cycling stability (13.4% capacitance fading after 5000 cycles). The outstanding overall performance is attributed to the synergistic effect of the NiCo₂S₄shell and NHSC core, which endows the composite with a stable structure, high electrical conductivity, abundant active reaction sites, and short ion-transport pathways. The synthesized NiCo₂S₄/NHCS composite is a competitive candidate for the electrodes of high-performance supercapacitors.