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A honeycomb-like structure nanocomposite composed of Ag nanoparticles doped NiMn-LDHs nanosheets shell and uniformly arranged Co 2 (OH) 2 CO 3 nanoneedles core shows promising electrochemical storage properties. [Display omitted] • Honeycomb-like CC@Co 2 CH/NM-LDH-Ag nanosheet arrays are synthesized on carbon cloth. • The hybrid of various active components provides abundant active sites and fast ion diffusion. • CC@Co 2 CH/NM-LDH-Ag is used to prepare binder-free electrodes and exhibits excellent electrochemical properties. • The assembled all-solid-state asymmetric supercapacitor shows high energy density and power density. Layered double hydroxides are considered promising electrode materials for the preparation of high-energy–density supercapacitors owing to their suitable microstructure and significant electrochemical properties. In this study, honeycomb-like NiMn-layered double-hydroxide (NiMn-LDH) nanosheet arrays with numerous electron/ion channels, a large number of active sites, considerable redox reversibility, and significant electrical conductivity were synthesized by combining Co 2 (OH) 2 CO 3 nanoneedle arrays with NiMn-LDH nanosheet arrays and Ag nanoparticles on a carbon cloth (CC) substrate through a hydrothermal strategy (CC@Co 2 CH/NM-LDH-Ag). The fabricated CC@Co 2 CH/NM-LDH-Ag binder-free electrode exhibited a high specific capacitance of 10,976 mF cm−2 (3092F/g, 1391.4C g−1) at 2 mA cm−2 (1 A/g), and a high capacitance retention of 93.2 % after 10,000 cycles at a current density of 20 mA cm−2. In addition, a solid-state asymmetric supercapacitor (ASC) device assembled using CC@Co 2 CH/NM-LDH-Ag as the cathode possessed an ultrahigh energy density of 68.85 Wh kg−1 at a power density of 722.6 W kg−1, and two fabricated ASC units in series were able to power a multifunctional display for more than 30 min. Therefore, this study provides a new approach for the design and synthesis of high-performance flexible electrodes. [ABSTRACT FROM AUTHOR]

Origami and layered-shaped ZnNiFe-LDH synthesized on Cu(OH) 2 nanorods array to enhance the energy storage capability. [Display omitted] The combination of layered nanorod arrays with unique core–shell structure and transition metal layered double hydroxide (LDH) is considered as a feasible solution to improve the electrochemical performances of capacitor electrode. In this study, layered ZnNiFe-LDH@Cu(OH) 2 /CF core–shell nanorod arrays, which consist of ultrathin ZnNiFe-LDHs nanosheet shells and ordered Cu(OH) 2 nanorod inner cores, are successfully designed and fabricated by a typical hydrothermal way and a simple in situ oxidation reaction. The electrode prepared using ZnNiFe-LDH@Cu(OH) 2 /CF nanomaterial reveals an remarkable area capacitance of 6100 mF cm−2 at 3 mA cm−2 current density, which is excellently superior than those of ZnFe-LDH@Cu(OH) 2 /CF, NiFe-LDH@Cu(OH) 2 /CF, Cu(OH) 2 /CF and CF. Additionally, the capacitance retention remains as high as 83.4% after 5000 cycles and a very small Rs (0.567 Ω) can be observed. In addition, an asymmetric supercapacitor device is successfully fabricated employing ZnNiFe-LDH@Cu(OH) 2 /CF. Meanwhile, the ZnNiFe-LDH@Cu(OH) 2 /CF//AC device can achieve an energy density of 44 Wh kg−1 and a corresponding power density of 720 W kg−1 and possess the capability to light up a multi-function monitor for 33 min just using two ASC equipments connected in series. Therefore, the prepared ZnNiFe-LDH@Cu(OH) 2 /CF composite materials with unique structure has great application potential in energy storage devices. [ABSTRACT FROM AUTHOR]

Ni 2 CoS 4 @(NiCo)Se 2 bimetallic selenides with core–shell heterostructure in-situ generated on Ni 2 CoS 4 nanorods arrays for high performance supercapacitors. [Display omitted] • Ni 2 CoS 4 @(NiCo)Se 2 composites with the core–shell structure are prepared by simple hydrothermal and in-situ selenization methods. • The synthesized electrode material exhibits good conductivity and a large specific surface area. • The assembled device has a high energy density (53 Wh kg−1) and power density (480 W kg−1). • Two assembled all-solid-state ASCs can light a 2.5 V LED lamp for 11 min. In this paper, Ni 2 CoS 4 @(NiCo)Se 2 /NF core–shell structural nanocomposites are successfully prepared on nickel foam (NF) substrates through a convenient hydrothermal method and tube furnace calcination. Firstly, NiCo 2 O 4 /NF is acquired by a one-step simple hydrothermal method and one-step tube furnace calcination, then it is sulfidated via a one-step hydrothermal method, and finally selenized by stirring to obtain Ni 2 CoS 4 @(NiCo)Se 2 /NF. The results show that in the three-electrode test, the specific capacitance of the Ni 2 CoS 4 @(NiCo)Se 2 electrode is able to reach 6054 mF·cm−2 at a current density of 10 mA·cm−2. The excellent performance of Ni 2 CoS 4 @(NiCo)Se 2 /NF nanocomposites is supposed to give rise to the bimetallic synergistic effect, as well as the unique core–shell structure of its surface-loaded nanosheets. In addition, all-solid-state asymmetric supercapacitors (ASCs) are composed of activated carbon (AC) as the anode and Ni 2 CoS 4 @(NiCo)Se 2 /NF as the cathode. The prepared Ni 2 CoS 4 @(NiCo)Se 2 /NF//AC ASC devices reach an energy density of 53 Wh kg−1 at a power density of 480 W kg−1. Simultaneously, Ni 2 CoS 4 @(NiCo)Se 2 /NF//AC ASC device has an excellent specific capacitance of 149.06F g−1 at a current density of 0.6 A/g and a capacitance retention rate of 84.0 % after 10,000 electrochemical cycles, which proves its good cycling stability. Impressively, two Ni 2 CoS 4 @(NiCo)Se 2 /NF//AC ASC devices connected in series can light up a 2.5 V LED lamp and continue to illuminate it for 11 min. Our results show that Ni 2 CoS 4 @(NiCo)Se 2 /NF nanocomposites with core–shell structures have great application potential in energy storage devices. [ABSTRACT FROM AUTHOR]

The excellent electrical conductivity of graphene is due to its highly‐conjugated structures. Manipulation of the electronic and mechanical properties of graphene can be achieved by controlling the destruction of its in‐sheet conjugation system. Herein, we report the preparation of CoCeSx−SA@BPMW@RGO through π‐π stacking interactions at the molecular level. In this study, sodium alginate was reacted with Co2+ and Ce3+, and the composite was loaded onto a graphene surface. The graphene sheets were prepared using a bi‐pyrene terminated molecular wire (BPMW) to avoid re‐stacking of the grapheme sheets, thereby forming nanoscale spaces between sheets. The angle between the BPMW coplanar pyrene group and the phenyl group was 33.2°, and the graphene layer is supported in an oblique direction. Finally, a three‐dimensional porous composite was obtained after annealing and vulcanization. The obtained CoCeSx−SA@BPMW@RGO exhibited excellent electrical conductivity and remarkable cycle stability. When the current density was 1 A g−1, its specific capacitance was as high as 1004 F g−1. BPMW modifies graphene through the synergistic effect of π‐π stacking interaction and special structure to obtain excellent electrochemical performance. Moreover, a solid‐state asymmetric supercapacitor device was fabricated based on the synthesized CoCeSx−SA@BPMW@RGO hybrid, which exhibited a power density of 979 W kg−1 at an energy density of 23.96 Wh kg−1. [ABSTRACT FROM AUTHOR]

Hierarchical CoSe 2 @NiMn-LDH@Cu 1.8 Se/CF nanosheet arrays with core-shell structure are synthesized via phase pseudomorphic transformation process achieved by selective selenization for Cu and Co elements for green chemistry energy storage. [Display omitted] As an emerging energy storage device, the practical application of supercapacitors (SCs) is currently constrained by their low energy density. Enhancing the capacitance of supercapacitors by leveraging the synergistic effect of multiple components in composite electrodes with well-designed structures can effectively increase their energy density. Here, a wire-sheet-particle hierarchical heterostructured CoSe 2 @NiMn-layered double hydroxide (NiMn-LDH) @Cu 1.8 Se/Copper foam (CF) electrode is synthesized via phase pseudomorphic transformation process achieved by selective selenization for Cu and Co elements. Benefiting from the stable support structure of CuBr 2 , the large specific surface area of NiMn-LDH, and the excellent conductivity of CoSe 2 , the prepared binder-free electrode shows excellent electrochemical properties. The CoSe 2 @NiMn-LDH@Cu 1.8 Se hybrid electrode exhibits a superior specific areal capacitance of 7064 mF cm−2 at 2 mA cm−2 and a stable cyclic performance with 80.11 % capacitance retention after 10,000 cycles. Furthermore, the assembled CoSe 2 @NiMn-LDH@Cu 1.8 Se/CF//AC (activated carbon) asymmetric supercapacitor (ASC) achieves an energy density of 36.6 Wh kg−1 when the power density is 760.6 W Kg−1 and retains 87.35 % of the initial capacitance after 5000 cycles. Overall, this pioneering research provided new insight for preparing supercapacitor electrode materials by selective selenization and ration design of the structures. [ABSTRACT FROM AUTHOR]

CeCoS x -SA/GF porous aerogels are fabricated based on sodium alginate with "egg-box" model and exhibited superior electrochemical properties as well as high mechanical strength. [Display omitted] • CeCoS x -SA/GF aerogels with "egg-box" structure is synthesized. • The CeCoS x -SA/GF electrode exhibits great electrochemical properties. • A portable multifunctional instrument can be powered for 28 mins. • Flexible CeCoS x -SA/GF/KOH/PVA film can be bent and twisted. • The CeCoS x -SA/GF/KOH/PVA film can lift 1 kg plastic bottle. Practical applications of flexible electrochemical energy storage devices are still limited by the lack of robust mechanical structures and high capacitive storage capabilities. Herein, the 3D CeCoS x -SA/GF porous aerogels are designed and prepared based on sodium alginate, which possess a special structure that can be explained by the so-called "egg-box" model. Each metal ion can be paired with the carboxyl and hydroxyl groups of the G monomer on two adjacent sodium alginate molecular chains. Melamine foam is used as carrier for graphene/sodium alginate impregnation and plays an important role on significantly limiting the agglomeration of graphene nanosheets due to their strong π-π stacking. The fabricated electrode based on CeCoS x -SA/GF shows an excellent electrochemical capacitance of 873.3F/g at the current density of 1A/g. In addition, the capacitance retention rate can still remain 87.1 % after 5000 cycles at a high current density of 8 A/g. Moreover, the fabricated all-solid state asymmetric supercapacitor device assembled with CoCeS x -SA/GF and active carbon shows an energy density of 29.58 Wh kg−1 at a power density of 801 W kg−1. For practical applications, the fabricated supercapacitor device can power a multifunctional display for 28 mins and illuminate a small light bulb for 3 mins. Moreover, the KOH/polyvinyl alcohol gel-electrolyte was used to fabricate high-strength and flexible CeCoS x -SA/GF/PVA/KOH composite film electrode, which can be bent at various angles (0°-180°) and can be twisted into various shapes. Notably, the CeCoS x -SA/GF/PVA/KOH composite film can lift plastic bottles containing 500 mL (500 g) and 1000 mL (1 kg) water, respectively, indicating that it has great application potential for wearable and portable electronic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] Ortho-hexagonal and highly-oriented NiMnCo-LDH/ZnO@CC self-supporting electrode derived from ZIF-67 covered ZnO nanorod-arrays is fabricated and employed for portable asymmetric solid-state supercapacitor. • Novel ortho -hexagonal NiMnCo-LDH has been synthesized. • ZIF-67 covered ZnO nanorod-arrays as self-supporting electrode is synthesized. • The fabricated electrodes exhibit superior electrochemical properties. • A multifunctional instrument can be powered for more than 30 mins. • The device can be carried outdoors to monitor time, temperature and air humidity. Metal-organic frameworks have attracted much attention due to their abundant redox sites and tunable characteristics, which are advantageous for energy storage applications. However, the low electrical conductivity, poor physical strength and undesirable capacity seriously hinder their applications. Therefore, designing effective and convenient strategies to build composites with unique structures will be of practical significance. Herein, we successfully generate NMC-LDH/ZnO@CC nanocomposites by growing ortho -hexagonal nickel–cobalt layered double hydroxide (NMC-LDH) nanosheets in-situ on ZIF-67 precursor covering vertical arrays of ZnO nanorods. As a result of the unqiue ortho -hexagonal structure, highly ordered arrangement of active substances and multi-dimensional spaces of the prepared NMC-LDH/ZnO@CC binder-free electrode, its capacitance is as high as 9258 mF cm−2 at a current density of 2 mA cm−2 and the capacitance retention is maintained at 87.5 % after 5000 cycles. Furthermore, in order to explore the practical value of the prepared binder-free electrode, the NMC-LDH/ZnO@CC//AC solid-state asymmetric supercapacitor device is assembled. The energy density of the assembled supercapacitor is 24.6 W h kg−1 at a power density of 170 W kg−1 and 1020 W kg−1 at an energy density of 11.8 W h kg−1. In addition, a versatile instrument for monitoring air humidity, time and ambient temperature in portable environments can be powered by a single ultracapacitor unit for more than 30 min. Overall, this study provides a unique strategy for synthesizing ZIF derivatives with novel morphologies for electrochemical energy storage applications. [ABSTRACT FROM AUTHOR]