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In this study, to fabricate a non-binder electrode, we grew nickel–cobalt sulfide (NCS) nanotubes (NTs) on a Ni foam substrate using a hydrothermal method through a two-step approach, namely in situ growth and an anion-exchange reaction. This was followed by the electrodeposition of double-layered nickel-cobalt hydroxide (NCOH) over a nanotube-coated substrate to fabricate NCOH core-shell nanotubes. The final product is called NCS@NCOH herein. Structural and morphological analyses of the synthesized electrode materials were conducted via SEM and XRD. Different electrodeposition times were selected, including 10, 20, 40, and 80 s. The results indicate that the NCSNTs electrodeposited with NCOH nanosheets for 40 s have the highest specific capacitance (SC), cycling stability (2105 Fg−1 at a current density of 2 Ag−1), and capacitance retention (65.1% after 3,000 cycles), in comparison with those electrodeposited for 10, 20, and 80 s. Furthermore, for practical applications, a device with negative and positive electrodes made of active carbon and NCS@NCOH was fabricated, achieving a high-energy density of 23.73 Whkg−1 at a power density of 400 Wkg−1. [ABSTRACT FROM AUTHOR]

Here, we report the extraordinary electrochemical energy storage capability of NiMoO4@NiMoO4 homogeneous hierarchical nanosheet-on-nanowire arrays (SOWAs), synthesized on nickel substrate by a two-stage hydrothermal process. Comparatively speaking, the SOWAs electrode displays superior electrochemical performances over the pure NiMoO4 nanowire arrays. Such improvements can be ascribed to the characteristic homogeneous hierarchical structure, which not only effectively increases the active surface areas for fast charge transfer, but also reduces the electrode resistance significantly by eliminating the potential barrier at the nanowire/nanosheet junction, an issue usually seen in other reported heterogeneous architectures. We further evaluate the performances of the SOWAs by constructing an asymmetric hybrid supercapacitor (ASC) with the SOWAs and activated carbon (AC). The optimized ASC shows excellent electrochemical performances with 47.2 Wh/kg in energy density of 1.38 kW/kg at 0–1.2 V. Moreover, the specific capacity retention can be as high as 91.4% after 4000 cycles, illustrating the remarkable cycling stability of the NiMoO4@NiMoO4//AC ASC device. Our results show that this unique NiMoO4@NiMoO4 SOWA has great prospects for future energy storage applications. [ABSTRACT FROM AUTHOR]

Desirable porous structure and huge ion-accessible surface area are crucial for rapid electronic and ionic pathway electrodes in high-performance graphene-based electrochemical capacitors. However, graphene nanosheets tend to aggregate and restack because of van der Waals interaction among graphene sheets, resulting in the loss of ion-accessible surface area and unsatisfactory electrochemical performance. To resolve this daunting challenge, a novel approach is developed for the self-assembly of holey graphene sheets intercalated with carbon spheres (H-GCS) to obtain freestanding electrodes by using a simple vacuum filtration approach and a subsequent KOH activation process. Through the introduction of carbon spheres as spacers, the restacking of reduced graphene oxide (rGO) sheets during the filtration process is mitigated efficiently. Pores on rGO sheets produced by subsequent KOH activation also provide rapid ionic diffusion kinetics and high ion-accessible electrochemical surface area, both of which favor the formation of electric double-layer capacitance. Furthermore, a higher degree of graphitization of CSs in H-GCS thin film improves the electrical conductivity of the H-GCS electrode. The H-GCS electrode exhibits 207.1 F g −1 of specific capacitance at a current density of 1 A g −1 in 6 M KOH aqueous electrolyte. Moreover, the symmetric electrochemical capacitor assembled with H-GCS electrodes and organic electrolyte is capable of delivering a maximum energy density of 29.5 Wh kg −1 and a power density of 22.6 kW kg −1 . [ABSTRACT FROM AUTHOR]

Abstract Rational design of electrode structures has been recognized as an effective strategy to improve the electrochemical performance of electrode materials. Herein, we demonstrate an integrated electrode in which nickel hydroxide (Ni(OH) 2) nanosheets are deposited on both sides of chemical vapor deposition-grown graphene on Ni foam, which not only effectively optimizes electrical conductivity of Ni(OH) 2 , but also accommodates the structural deformation associated with the large volume change upon cycling. The synthesized Ni(OH) 2 /graphene/Ni(OH) 2 /Ni foam electrode exhibits a high specific capacity of 991 C g−1 at a current density of 1 A g−1, which is higher than the theoretical specific capacity of additive sum of Ni(OH) 2 and graphene, and retains 95.4% of the initial capacity after 5000 cycles. A hybrid supercapacitor is constructed by using Ni(OH) 2 /graphene/Ni(OH) 2 /Ni foam as the positive electrode and activated carbon on Ni foam as the negative electrode, which achieves a maximum energy density of 49.5 W h kg−1 at a power density of 750 W kg−1, and excellent cycling lifespans with 89.3% retention after 10000 cycles at 10 A g−1. [ABSTRACT FROM AUTHOR]

Abstract Rational electrode architectural design, favorable electrode composition, and versatile synthesis approach play a significant role in developing advanced electrodes for high-performance supercapacitor. In this work, we report a facile approach for fabricating 1D hierarchical CuO@Co x Ni 1−x (OH) 2 nanowire arrays grown on 3D highly conductive copper foam. The optimized CuO@Co 0.2 Ni 0.8 (OH) 2 electrode delivers an ultrahigh specific capacity of 374.7 mAh g−1 at 2 A g−1 with exceptional rate capability (301.7 mAh g−1 at 50 A g−1) and remarkable cycling stability (95.9% after 10 000 cycles at 50 A g−1). A flexible asymmetric solid-state supercapacitor (ASC) is fabricated using the optimized CuO@Co 0.2 Ni 0.8 (OH) 2 as the positive electrode, activated carbon-coated nickel foam as the negative electrode, and polyvinyl alcohol/KOH gel as electrolyte. The flexible ASC operating with a potential window of 0–1.6 V delivers an energy density of 46.5 Wh kg−1 with a power density of 526.9 W kg−1. The ASC also exhibits excellent cycling stability with a capacity retention of 84.3% after 10 000 cycles at a current density of 7 A g−1. Graphical abstract Image 1 Highlights • CuO@Co x Ni 1−x (OH) 2 nanowire arrays grown on 3D copper foam was fabricated. • The architecture delivered an ultrahigh specific capacity. • Flexible hybrid supercapacitor using CuO@Co 0.2 Ni 0.8 (OH) 2 was assembled. • The flexible devices displayed excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

Herein, we report 3D broccoli-like nanoflowers of SnS on Ni foam (SnS/NF) using an easy chemical method and explore their use as binder free electrode in supercapacitor. As-synthesized electrode material was characterized by X-ray diffractometer (XRD), Field emission scanning electron microscope (FESEM), energy dispersive spectroscopy (EDS) and transmission electron microscope (TEM). As-fabricated SnS/NF electrode exhibited redox behavior with excellent specific capacitance of 1102 F g−1 at a current density of 5 A cm−2 as well as high rate capability of 61.7% up to 30 A cm−2. These findings make SnS/NF a better alternative source for energy storage devices. • Novel Broccoli-like 3D nanoflowers of SnS is synthesized by solvothermal route. • 3D arrangement in SnS nanoflowers is comprised by ultra-thin 2D nanosheets. • SnS/NF electrode exhibits excellent specific capacitance of 1102 F g-1. • Superior cycling stability and rate capability is shown by as-fabricated electrode. [ABSTRACT FROM AUTHOR]

• Carbon composited with pseudocapacitive material emerged with great interest. • The electrochemical performance of hybrid composites is discussed systematically. • This review provides a comprehensive study. • Future perspectives and challenges in practical application also discussed. Supercapacitors are considered reliable devices for energy storage. However, supercapacitor has some limitations, such as relatively low capacitance and low energy density, which affect it as a promising energy storage device. In this context, carbon based nanocomposites have been widely studied in the past few years due to their excellent physical, mechanical and electrical properties. A lot of studies have been reported on carbon based materials with different 0D, 1D, 2D and 3D carbon nanostructures. The unique combination of pseudo-material with carbon material greatly improves the electrochemical performance of the composite as compared to individual candidate. However, developing high energy density supercapacitor devices with high cycling stability in a simple and cost effective way is still a challenge. This review provides the current progress on the carbon based pseudo-material composites for supercapacitor application in a well-systematic and easy manner which can guide the early researchers and emerging scientists dealing with or interested in supercapacitor. [ABSTRACT FROM AUTHOR]