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[Display omitted] • MgCo 2 O 4 @NiMn-LDH core-shell nanoarrays is fabricated on Ni foams. • The materials are obtained by a facile hydrothermal strategy. • MgCo 2 O 4 @NiMn-LDH electrode exhibits superb supercapacitive performance. In this work, MgCo 2 O 4 @NiMn layered double hydroxide (LDH) core-shell structured nanocomposites on Ni foam (NF) are synthesized by facile hydrothermal and calcination methods. MgCo 2 O 4 /NF is synthesized first via a hydrothermal reaction and annealing treatment, and then utilized to prepare MgCo 2 O 4 @NiMn-LDH/NF core-shell structured nanocomposites via the second hydrothermal process. It is found that the MgCo 2 O 4 @NiMn-LDH/NF nanocomposite prepared from 6 h hydrothermal reaction (MC@NM-LDH-2) exhibits an excellent specific capacitance of 3757.2 F g−1 (at 1 A g−1). Moreover, a high capacitance retention (86.9% after 6000 cycles) and a low internal resistance (Rs) (0.565 Ω) can be achieved. Furthermore, an all-solid-state asymmetric supercapacitor (ASC) is assembled using MgCo 2 O 4 @NiMn-LDH/NF-2 as positive electrode and activated carbon (AC) as negative electrode. The as-fabricated MgCo 2 O 4 @NiMn-LDH/NF-2//AC ASC shows a high energy density of 62.33 Wh kg−1 at 750 W kg−1. Meanwhile, the MgCo 2 O 4 @NiMn-LDH/NF-2//AC ASC device possesses an outstanding cycling stability of 93.7% retention of the initial capacitance after 6000 cycles and three ASC devices connected in series can light up a LED bulb for 15 min. Our results manifest that these core-shell structure MgCo 2 O 4 @NiMn-LDH nanocomposites could envision huge potential application in energy storage devices. [ABSTRACT FROM AUTHOR]

In this work, for the first time we are reporting the development of a kind of high rate and long cycle life electrode composed of nickel cobalt manganese ternary carbonate hydroxide (NiCoMn-CH) ultrathin nanoflakes coated on Co-CH nanowire arrays (NWAs), which are directly generated on a nickel foam (NF) support. The hierarchical heterostructures are synthesized via a scalable two step solvothermal strategy without any adscititious surfactant and binder. The smart combination of Co-CH and NiCoMn-CH nanostructures in the nanowire arrays shows significant synergistic effect on the enhancement of the electrochemical performance of the as-fabricated supercapacitors. The as-obtained electrode exhibits excellent conductivity and high specific surface area, resulting in an unprecedented high specific capacitance (up to 3224 F g−1 at 1 A g−1 in a three-electrode system) and an ultralong cycling stability (92.4% retention after 6000 successive charge–discharge cycles 5 A g−1). Meanwhile, an asymmetric supercapacitor device assembled of the Co-CH@NiCoMn-CH hierarchical nanostructures as positive electrode and activated carbon (AC) as negative electrode delivers good energy density of 20.31 W h kg−1 at the power density of 748.46 W kg−1 in the operation window 0–1.5 V. This methodology could be generalized to the design of other novel structured nanomaterials for energy storage devices and other applications. [ABSTRACT FROM AUTHOR]

Trimetallic sulfide microspheres with flower morphology prepared based on novel bimetallic MOF via sequential ion exchange processes exhibit promising energy storage properties. Rational design of electrical active materials with high performance for energy storage and conversion is of great significance. Herein, Cu(NiCo) 2 S 4 /Ni 3 S 4 , a three-dimensional (3D) hierarchical hollow heterostructured electrode material, is designed by etching the well-defined bimetal organic framework (MOF) via sequential in-situ ion-exchange processes. This trimetallic sulfides with unique structure provide large surface area, hierarchical pore distribution and enhanced electrical conductivity, can enrich the active sites for redox reactions, facilitate electrolyte penetration and rapid charge transfer kinetics. As a result, the Cu(NiCo) 2 S 4 /Ni 3 S 4 electrode exhibits a high specific capacitance of 1320 F/g at 1 A/g and excellent rate performance (only 15% of capacitance is attenuated when the current density is increased by 20 times). Furthermore, a fabricated hybrid supercapacitor of Cu(NiCo) 2 S 4 /Ni 3 S 4 /AC can deliver a maximum energy density of 40.8 Wh/kg, remarkable power density of 7859.2 W/kg and superior cycling stability (85% retention of capacitance after 5000 cycles), demonstrating great potential for practical applications in energy storage and conversion devices. [ABSTRACT FROM AUTHOR]

Manganese dioxide (MnO 2) with high theoretical capacity (1380 F g−1), high natural abundance and low cost has been considered as one of the most competitive active materials for preparing the electrode of supercapacitors. However, the poor electrical conductivity limits its broad applications. To solve this problem, we design a hierarchical Cu(OH) 2 @MnO 2 core-shell nanorods array on copper foam (CF), in which the one-dimensional (1D) Cu(OH) 2 nanorod core provides the scaffold for the growth of MnO 2 nanosheets and a short ion and electronic diffusion pathway and the two-dimensional (2D) MnO 2 nanosheets shell provides enormous active sites due to their large surface area. The obtained Cu(OH) 2 @MnO 2 /CF nanorods array displays an excellent areal capacitance of 708.62 mF cm−2 at the current density of 2 mA cm−2 (283.45 F g−1 at 0.8 A g−1). Additionally, the assembled Cu(OH) 2 @MnO 2 /CF//activated carbon (AC) asymmetric supercapacitor shows an outstanding energy density of 18.36 Wh kg−1 at a power density of 750 W kg−1. Two such capacitors connected in series can light up a red LED bulb for over fifteen minutes. [ABSTRACT FROM AUTHOR]

Herein, we designed and prepared nickel metal-organic framework microspheres anchored directly on reduced graphene oxide (Ni-MOF/rGO) by a facile hydrothermal and successive calcining process. The electrode for Ni-MOF/rGO composite annealed at an optimized temperature of 300 °C (Ni-MOF/rGO-300) shows desired conductivity, good cycling stability and high ion-accessible surface area, leading to an ultrahigh specific capacitance of 954 F g−1 at a current density of 1 A g−1 and a remarkable rate capability of 80.25% at 5 A g−1. Meanwhile, the assembled Ni-MOF/rGO-300//activated carbon asymmetric supercapacitor (ASC) shows a favorable energy density up to 17.13 Wh kg−1 at a power density of 750 W kg−1 in the potential window of 0–1.5 V. Moreover, the capacitance retention can still maintain 81.63% after 4000 cycles at a high current density of 5 A g−1. The excellent electrochemical properties can be credited to the synergistic effects between the unique structures of Ni-MOF and rGO, which makes the Ni-MOF/rGO composite a potential electrode material for high performance supercapacitors. [ABSTRACT FROM AUTHOR]

Direct generation of active materials on carbon cloth (CC) is regarded as an efficient and convenient means to obtain flexible electrodes with high supercapacitor performance. However, uniform generation of active materials on the both sides of CC remains a great challenge. Herein, a facile hanging-hydrothermal method was used to directly generate uniform NiCo 2 S 4 nanosheet arrays on carbon cloth (NiCo 2 S 4 /CC), which was then utilized as the positive electrode for flexible supercapacitors. Taking advantage of the unique and uniform honeycomb-like structure of NiCo 2 S 4 nanosheets, the obtained NiCo 2 S 4 /CC electrode can deliver an excellent specific capacitance (1638 F g−1 at 1 A g−1), which is significantly higher than NiCo 2 O 4 /CC electrode (657.4 F g−1 at 1 A g−1). A two-electrode flexible supercapacitor was assembled using NiCo 2 S 4 /CC as positive electrode and carbon cloth coated with activated carbon as negative electrode and revealed a high energy density of 25.2 Wh kg−1 at a power density of 799.6 W kg−1, highlighting its great potential for flexible supercapacitor applications. [ABSTRACT FROM AUTHOR]

The hollow and spinous NiCo 2 S 4 nanotubes were designed and prepared through hydrothermal sulfurization reaction using the degummed natural cocoon silk as a template. Recently, ternary cobalt nickel sulfide, performing as the promising electrode material for supercapacitors has obtained great interests. Herein, the hollow and spinous NiCo 2 S 4 nanotubes are designed and prepared through a simple hydrothermal reaction using the natural silk as the template. The spinous Ni-Co precursors are grown on the natural silk through a facile hydrothermal strategy and the hollow structure is obtained by decomposing the silk via hydrothermal sulfurization. After the calcination treatment, the hollow and spinous NiCo 2 S 4 nanotubes are applied as the electrode material and exhibit better electrochemical performance than the solely vulcanized samples. In addition, owing to the unique hollow and spinous structure of NiCo 2 S 4 nanotubes, the supercapacitor electrode material shows good specific capacitance (630 F g−1 at 1 A g−1), low internal resistance R s (0.68 Ω) and high capacitance retention (91% after 3000 cycles) at 10 A g−1. Furthermore, an all-solid-state asymmetric supercapacitor is self-assembled with the SC400 composite and exhibits an energy density of 52.34 Wh kg−1 at the power density of 2206.37 W kg−1. Additionally, a blue LED indicator can be powered by connecting two ASCs in series. The prepared hollow and spinous NiCo 2 S 4 nanotubes with excellent electrochemical properties can envision promising applications in energy storage devices and nanotechnology. [ABSTRACT FROM AUTHOR]