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Cobaltous oxide/nickel–iron oxide (Co3O4/NiFe2O4) hybrids were fabricated via a template-free hydrothermal route with cyclodextrin as a reactor and a further two-step annealing treatment in an air atmosphere. The hybrid is composed of many small nanoparticles with a particle size distribution range from 20 to 50 nm. The hybrid combined the advantages of Co3O4 and NiFe2O4 nanoparticles, presenting enhanced electrochemical properties than its single component. The Co3O4/NiFe2O4 (0.6:1) hybrid electrode exhibited the highest specific capacitance and great electrochemical cycle stability (over 90.7% of total capacitance at 2 A g−1 after 1000 cycles and still kept 84.6% at 5 A g−1 after 5000 cycles). This may be ascribed to the common contribution of each component, which not only provided good electronic conductivity for efficient charge transfer but also a stable structure for better ions diffusion. A Co3O4/NiFe2O4//AC asymmetry supercapacitor was assembled and manifested the highest energy density of 76.0 Wh kg−1 at a power density of 859.7 W kg−1 and still kept 37.3 Wh kg−1 at the highest power density of 6.0 kW kg−1. This work indicated that the Co3O4/NiFe2O4 hybrid should be a potential active material for the electrochemical application. [ABSTRACT FROM AUTHOR]

Abstract The ever-increasing concerns about global environmental problems and depletion of fossil resources have stimulated intensive research on low-cost and high-performance energy storage materials. Here, we introduce the two-step sulfidation of hierarchical ferric-cobalt sulfide hollow nanoneedles on electrical conductive carbon fiber paper (CFP) for high-performance supercapacitor electrodes. Under the growth regulation of macroporous CFP substrate, prepared free-standing composite paper with tip-welded ferric-cobalt sulfide hollow nanoneedles can offer substantial exposed electroactive sites for Faradaic redox reaction and effectively buffer the drastic volume change during long-term charge-discharge, and also provide fast charge transfer paths through the carbon skeleton for efficient energy storage. Due to these unique features, obtained composite paper electrode delivers a higher specific capacitance (2282 F g−1 at current density of 1 A g−1) than those of the previously reported MCo 2 S 4 based electrodes. Asymmetric supercapacitor assembled using the composite paper as the binder-free positive electrode also shows a high energy density of 86.8 Wh kg−1 at a power density of 800 W kg−1, and an impressive 82.3% capacitance retention after 5000 cycles, demonstrating the great potential of this low-cost and free-standing electrodes towards high-performance energy storage. [ABSTRACT FROM AUTHOR]

The ever-increasing requirements for renewable energy supply have pushed forward the development of low-cost and high performance energy storage systems. Here, we introduce the facile synthesis of a membrane-like electrode material by the uniform deposition of ultrathin NiMoO 4 nanosheets on carbon nanofiber (CNF) membrane through electrospinning and solvothermal reaction. Under the templating of macroporous CNF substrate, obtained hierarchical CNF/NiMoO 4 composite membrane with perpendicularly grown NiMoO 4 nanosheets can offer substantial exposed electroactive sites for Faradaic redox reaction, and also provide interconnected conducting CNF networks for efficient charge transfer. Benefiting from these unique characteristics, the CNF/NiMoO 4 composite membrane electrode exhibits a high specific capacitance of 1675 F g -1  at 1 A g −1 , which outperforms most of the previously reported NiMoO 4 -based electrodes. Moreover, the asymmetric supercapacitor device is also fabricated utilizing the CNF/NiMoO 4 composite membrane as the binder-free positive electrode, which also delivers a superior cycling stability (83.6% capacity retention after 3000 cycles) and high energy density of 44.4 Wh kg −1 at a power density of 800 W kg −1 . Hence, current study provides a new protocol for the low-cost fabrication of membrane-like electrodes towards practical supercapacitor applications. [ABSTRACT FROM AUTHOR]

A 3D hierarchical NiCo2O4/PANI/MF composite foam with a macroporous 3D skeleton, a conductive PANI coating and highly electrochemically active NiCo2O4 nanosheets is synthesized as a lightweight and low-cost electrode material. Due to the collaborative contribution of all the components, the prepared composite foam exhibits excellent capacitive performances when incorporated into an asymmetric supercapacitor. [ABSTRACT FROM AUTHOR]

A series of core-triple-shelled GCNF/PANI/NCO nanostructures have been fabricated via a facile strategy. Taking full advantage of the free-standing architecture of graphene-coated electrospun carbon nanofibers (GCNF), high conductivity and flexibility of the polyaniline (PANI) layers, and abundant active sites of nickel carbonate hydroxide (Ni 2 (CO 3)(OH) 2) nanosheets, the optimal electrode exhibits a high specific capacitance of 1565F g−1 at 1 A/g, which exceeds almost all of the reported nickel carbonate hydroxide-based electrodes in literatures. A hybrid supercapacitor delivers a high energy density of 35.4 Wh kg−1@750 W kg−1 and a long cycle lifespan. This strategy enables the controllable synthesis of core-triple-shelled hierarchical materials applicable to diverse electrochemical applications. [Display omitted] • We prepared the core-triple-shelled GCNF/PANI/NCO fiber-based films via a new route. • The optimal electrode exhibits high electrochemical properties via joint actions. • A hybrid supercapacitor displays large specific capacities and high energy density. • This strategy provides a new way to synthesize other core-triple-shelled materials. Designing novel efficient electrode materials with controlled hierarchical structure and composition for advanced supercapacitors remains a great challenge. Herein, a core-triple-shelled hierarchical GCNF/PANI/NCO nanostructure has been designed and fabricated by sequential growth of the conductive polyaniline (PANI) layers and nickel carbonate hydroxide (Ni 2 (CO 3)(OH) 2) nanosheets on the graphene-coated electrospun carbon nanofibers (GCNF) via a facile wet-chemical strategy. Taking full advantage of the free-standing architecture of graphene-coated electrospun carbon nanofibers, high conductivity and flexibility of the PANI layers, and abundant active sites of Ni 2 (CO 3)(OH) 2 nanosheets, the optimal GCNF/PANI/NCO (2 h) electrode exhibits a high specific capacitance of 1565F g−1 at 1 A/g and enhanced rate capability, which are higher than those of the GCNF, GCNF/PANI, and GCNF/NCO (2 h) electrodes at the same situation, and also exceeds most of the reported nickel carbonate hydroxide-based electrodes in literature. The superior performance should be mainly ascribed to the collaborative contribution of each component. Moreover, a self-assembled GCNF/PANI/NCO//AC hybrid supercapacitor delivers a high energy density of 35.4 Wh kg−1@750 W kg−1 and a long cycle lifespan. This strategy enables the controllable synthesis of core-triple-shelled hierarchical materials applicable to advanced electrochemical applications. [ABSTRACT FROM AUTHOR]

Engineering nanostructured architecture with a hierarchically arranged active surface is regarded as an effective strategy to develop advanced electrode materials. Herein, nanosheet-built MnCo 2 S 4 micro-disks with abundant nano-pores are synthesized and uniformly dispersed on a three-dimensional nitrogen-doped carbon matrix (3DNC). In the resultant 3DNC@MnCo 2 S 4 composite architecture, N-doped carbon network provides interconnected and shortened pathways for fast ion transmission and charge transfer, and the nanosheet-built MnCo 2 S 4 disks allow the efficient Faradaic redox process through the increased active surface. Due to the compositional and structural advantages, prepared 3DNC@MnCo 2 S 4 composite architecture delivers a superior electrochemical capacitive performance than 3DNC@MnCo 2 O 4 and other sulphospinel-based electrodes (including a high specific capacitance of 1812 F g−1 at 1A g−1, and a high rate performance of 82.9% capacitance retention at 20 A g−1). When assembled into hybrid supercapacitor device, the 3DNC@MnCo 2 S 4 //AC HSC also exhibits a high energy density of 68.8 Wh kg−1 at the power density of 800 W kg−1 and excellent cycling stability (82% capacitance retention after 5000 cycles at the current density of 10 A g−1). The facile yet efficient construction of this 3D porous electrode provides an innovative method for developing high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

Recently, nickel ferrite with high theoretical capacity over the other metal oxide has been applied as electrode material for batteries and supercapacitors. However, owing to the serious aggregation and low specific surface area, the electrochemical performance of nickel ferrite (NiFe 2 O 4 ) should be in urgent need of improvement. Here, we report the synthesis of unique molybdenum dioxide (MoO 2 ) and nickel ferrite composite (MoO 2 /NiFe 2 O 4 ) material via a facile strategy for the first time. The composite material presents a nanosheets-nanocrystals heterostructure. When evaluated as an electrode for hybrid supercapacitor in an alkaline solution, the MoO 2 /NiFe 2 O 4 composite material presents a greatly enhanced specific capacity (2105 mA h/g at 4 A/g), which is better than those of individual component and exceeds some of the reported MoO 2 and NiFe 2 O 4 based electrodes. The capacity retention of MoO 2 /NiFe 2 O 4 composite is about 81.1% after 1900 cycles. Such composite material also has great potential in other energy storage and conversion system. [ABSTRACT FROM AUTHOR]

A new tendency in supercapacitor research has focused on the construction of the inexpensive electrode materials with long cycle stability. In this study, TiO 2 /C 3 N 4 hybrid materials are synthesized through an efficient, low-cost, facile hydrothermal approach followed by a heat treatment for the first time. The hybrid materials are further used as electrodes for supercapacitors. Interestingly, compared to pure TiO 2 nanoparticles, TiO 2 /C 3 N 4 hybrid materials exhibit excellent electrochemical performance with improved specific capacitance, great rate performance and cycling stability (capacitance retention of 100% after 1000 cycles), which can be attributed to good conductivity and low polarization resulting in a high utilization of active materials. Furthermore, it was found that the capacitive properties of TiO 2 /C 3 N 4 hybrid were related to the pore sizes and electrical resistances of active materials. The electrode materials with smaller pore size and resistance showed higher capacitive properties. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amorphous/crystalline FC@MS-EG heterostructure is prepared via an EG-induced method. • The flexible electrode presents high specific capacitance and capacitance retention. • The superiority of FC@MS-EG is discussed by chemical analysis and DFT calculation. • An asymmetric device shows ultrahigh energy density (88.09 Wh kg−1@750 W kg−1). Although flexible supercapacitors have important applications, the development of high-performance flexible supercapacitors still remains a critical challenge owing to the low ion diffusion rate, poor electro-conductivity, and limited active defect sites. Herein, we report the first amorphous MoS x nanoparticles grown on crystalline FeCo-based nanoneedles (FC@MS-EG) via an ethylene glycol-induced strategy. The FC@MS-EG electrode presents an unprecedented specific capacitance of 1956 F g−1 at 1 A g−1 and over 91.1% of capacitance retention even after 6000 cycles because of the unique morphology, the rich defect sites, the high carrier concentration. The FC@MS-EG//AC asymmetric supercapacitor delivers an ultrahigh specific capacitance of 282 F g−1 at 1 A g−1 and an excellent energy density of 88.09 Wh kg−1 along with a power density of 750 W kg−1. And the self-assembled flexible all-solid-state supercapacitor device can be easily bent and twisted with negligible electrochemical properties attenuation. [ABSTRACT FROM AUTHOR]

NiS/MoS 2 composite nanosheets were designed and prepared via facile ion-exchange, freeze-drying, and Ostwald ripening processes. MoS 2 nanosheets served as backbones to absorb Ni2+ ions and form NiS nanosheets. The electrode based on the NiS/MoS 2 composite nanosheets exhibited an ultrahigh specific capacity of 343.5 mA h g−1 at 9 A g−1, which was superior to that of as-prepared MoS 2 nanosheets (125.8 mA h g−1) and Ni(OH) 2 nanosheets (148.9 mA h g−1). In addition, NiS/MoS 2 composite nanosheets presented an enhanced rate performance and good life cycle due to their hierarchical structure, high surface area with numerous active sites, and synergistic performance. A NiS/MoS 2 //AC asymmetric supercapacitor device operated in a large potential window (0–1.5 V) delivered a high capacitance of 48.4 F g−1 at 0.1 A g−1, an excellent energy density of 15.1 Wh kg−1 and a very high power density of 2.25 kW kg−1. This smart in situ construction process opens a new route to synthesize binary metal sulfides for high-performance energy storage devices. • NiS/MoS 2 nanosheets were prepared via an ion-exchange process and Ostwald ripening. • The composite exhibits an ultra-high specific capacity and cycle lifespan. • The results were ascribed to the high surface area and low contact resistance. • A NiS/MoS 2 //AC ASC device shows excellent energy densities. [ABSTRACT FROM AUTHOR]

Unique molybdenum trioxide decorated nickel-cobalt oxide nanostructures (MoO 3 /NiCo 2 O 4 -NSs) and three-dimensional hierarchical structure α-FeOOH/rGO film were prepared via facile hydrothermal and annealing strategies. Owing to the merits of the large surface area, superior ionic conductivity, increased availability of active sites/interfaces, rich mixed valences of polymetallic oxide and the favorable structural stability, the as-prepared optimized battery-type MoO 3 /NiCo 2 O 4 -NSs electrode material presents an extraordinary specific capacity (1042 F g−1 at 1 A g−1), largely improved rate capability (93%, from 1 to 6 A g−1), and superior cycling performance, compared with the NiCo 2 O 4 –NCs, MoO 3 , and also exceeds some of the reported Ni-, Co-based electrodes. Underlying such great improvement, a MoO 3 /NiCo 2 O 4 -NSs//α-FeOOH/rGO asymmetric supercapacitor device with a large potential window was assembled, which delivered a high capacitance of 141 F g−1 at 1 A g−1, an excellent energy density of 50.2 Wh kg−1, and an amazing power density of 4.8 kW kg−1. The serially connected asymmetric supercapacitor can power commercial light-emitting diodes suggesting their potential application for electronic gadgets. The superior energy storage characteristics of the asymmetric supercapacitor are strongly attributed to the interconnected 3D nanoporous network architectures of the MoO 3 /NiCo 2 O 4 -NSs and the good compatibility with the α-FeOOH/rGO negative electrode. Unique MoO 3 /NiCo 2 O 4 -NSs and α-FeOOH/rGO film were successfully synthesized for supercapacitor applications. The optimized MoO 3 /NiCo 2 O 4 -NSs electrode presents a high specific capacity (1042 F/g at 1 A/g), improved rate performance (93%, from 1 A/g to 6 A/g), and superior cycling performance (110% capacitance retention after 2000 cycles). A MoO 3 /NiCo 2 O 4 -NSs//α-FeOOH/rGO asymmetric supercapacitor delivered an excellent energy density (50.2 Wh kg−1) and an amazing power density (4.8 kW kg−1). Image 1 • MoO 3 /NiCo 2 O 4 -NSs and α-FeOOH/rGO were prepared via a simple wet-chemical strategy. • MoO 3 /NiCo 2 O 4 -NSs show high surface area, fast ion transfer, and good structural stability. • MoO 3 /NiCo 2 O 4 -NSs presented enhanced specific capacity, rate, and cycling performance. • An ASC device exhibited a high capacity with a wide potential window. • MoO 3 /NiCo 2 O 4 -NSs//α-FeOOH/rGO delivered an ultrahigh energy density of 50.2 Wh kg−1. [ABSTRACT FROM AUTHOR]