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The synthesis of layered nanorod arrays with a core‐shell structure is considered to be a viable strategy to improve the electrochemical property of electrode materials. Herein, we have successfully designed and fabricated layered MoO3‐MnNi LDH@Cu(OH)2/CF(MO‐MN LDH@COH) core‐shell nanorods through a handy in‐situ oxidation reaction followed by a hydrothermal synthesis, which consist of ordered Cu(OH)2 nanorods and ultra‐thin MoO3‐MnNi LDHs nanosheets. The MO‐MN LDH@COH which is utilized as the cathode in three electrodes exhibits superior electrochemical property. The specific capacity of prepared electrode is 16913 mF cm−2 under a current density of 2 mA cm−2, which is superior to its counterparts of COH, MN LDH@COH‐0, MO‐MN LDH@COH‐0.5 and MO‐MN LDH@COH‐2. What's more, the cycling stability reaches 83.33 % capacitance retention after 5000 cycles under the current density of 30 mA cm−2. When a solid‐state asymmetric supercapacitor (ASC) device (MO‐MN LDH@COH//AC) is fabricated, it could keep a household LED screen running for 27 minutes, verifying the immense commercial potential. Overall, this unique MO‐MN LDH@COH nanocomposite with excellent electrochemical performance should envision great practical application potential. [ABSTRACT FROM AUTHOR]

In this work, the densely distributed and core‐shell structured Cu(OH)2@NiFe‐LDH nanoarrays on copper foam (COH@NF‐LDH/CF) are constructed by a facile and feasible in situ oxidation method combined with potentiostatic electrodeposition. This distinct core‐shell structure as well as the synergetic effect between Cu(OH)2 and NiFe‐LDH provides a tremendous advantage, such as sufficient chemical active spots, the pathway for electron and ion transfer, to enhance the electrochemical performance of COH@NF‐LDH/CF. In particular, the area capacitance of synthesized COH@NF‐LDH/CF can reach 4.139 F cm−2 at 5 mA cm−2, which remarkably precede the single bare Cu(OH)2 (198 mF cm−2) or NiFe‐LDH/CF (71 mF cm−2) electrode materials at the same current density. Furthermore, the sample COH@NF‐LDH/CF is investigated and found to have excellent cycle stability (maintained 86.47 % after 5000 cycles). More importantly, the COH@NF‐LDH/CF electrode also can be utilized directly as the positive electrode and activated carbon (AC) as the negative electrode to assemble a facile asymmetric supercapacitor, which achieves a voltage window of up to 1.5 V and demonstrate up 65.56 Wh kg−1 brilliant energy density under 750 W kg−1. Therefore, their results indicate that COH@NF‐LDH/CF core‐shell structure nanocomposites may have a great prospect of application in energy storage. [ABSTRACT FROM AUTHOR]

The fascinating search for ultraefficient and high‐powered supercapacitors has stimulated continuous exploration of diverse energy storage materials like transition metal hydroxides with core–shell structure. Thus in this paper, a novel core–shell hybrid electrode material of nickel hydroxide (Ni(OH)2) supported on copper hydroxide nanorod arrays (Cu(OH)2 NAs), which is constructed on copper foam as the substrate by an in situ chemical oxidation reaction accompanied by chemical bath deposition, is reported. As a result, it is found that the pre‐fabricated Cu(OH)2@Ni(OH)2 electrode has a remarkable areal capacitance of 9.27 F cm−2 and good cycling performance (retains 92.38% after 6000 cycles) compared to its counterpart Cu(OH)2 nanorods (88.57%). Additionally, the Cu(OH)2@Ni(OH)2 material, as a positive electrode, can also be used to assemble a hybrid supercapacitor (HSC) while activated carbon is chosen as the negative electrode. As a result, the constructed HSC device with the desired working voltage of 0–1.5 V can light up the light‐emitting diode indicator, proving the potential practicability of the pre‐fabricated HSC device. [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]

MXenes, 2D transition metal carbides, and nitrides have attracted tremendous interest because of their metallic conductivity, solution processability, and excellent merits in energy storage and other applications. However, the pristine MXene films often suffer from poor ambient stability and mechanical properties that stem from their polar terminal groups and weak interlayer interactions. Here, a heteroatom doping strategy is developed to tailor the surface functionalities of MXene, followed by the addition of large‐sized reduced graphene oxide (rGO) as conductive additives to achieve a scalable production of S, N‐MXene/rGO (SNMG‐40) hybrid film with high mechanical strength (≈45 MPa) and energy storage properties (698.5 F cm−3). Notably, the SNMG‐40 film also demonstrates long‐term cycling stability (≈98% capacitance retention after 30 000 cycles), which can be maintained under ambient condition or immersed in H2SO4 electrolyte for more than 100 days. The asymmetric supercapacitor (aMGSC) based on SNMG‐40 film shows an ultrahigh energy density of 22.3 Wh kg−1, which is much higher than those previously reported MXene‐based materials. Moreover, the aMGSC also provides excellent mechanical durability under different deformation conditions. Thus, this strategy makes MXene materials more competitive for real‐world applications such as flexible electronics and electromagnetic interference shielding. [ABSTRACT FROM AUTHOR]

The study of metal–organic framework (MOF) as supercapacitor materials has attracted much attention. Here, a novel vapor‐phase approach is developed to in situ grow arrays of Cu2+1O (Cu2O with metal excess defects) @Cu‐MOF clusters on copper foam (CF) from the well‐aligned Cu(OH)2 nanorods in response to the exposure in the ligand gas. Benefiting from highly oriented and hierarchical structure of Cu‐MOF clusters arrays, synergistic effect between Cu2+1O and Cu‐MOF, and intimate connection of Cu2+1O@Cu‐MOF and CF, the Cu2+1O@Cu‐MOF/CF displays enhanced specific capacitance compared to Cu(OH)2/CF and Cu2+1O/CF (≈2.5 F cm−2 vs ≈0.8 and 0.9 F cm−2 at 2 mA cm−2). The quantitative analysis reveals that the capacitance of the Cu2+1O@Cu‐MOF/CF is largely contributed by the surface capacitive processes, consisting of double‐layer capacitance coming from porous Cu‐MOF and Faradaic capacitance rooting from Cu ion. The asymmetric supercapacitor of Cu2+1O@Cu‐MOF/CF//AC achieves high energy density of 38.3 Wh kg−1 at power density of 824.6 W kg−1 with capacitance retention of 90% after 5000 cycles. This study provides new avenue for in situ growth of MOF as electrodes for supercapacitors, by directly using high conductive metal as precursor through vapor‐phase approach, rather than traditional combination of linkers and metal salts in organic solvent. [ABSTRACT FROM AUTHOR]

Supercapacitors have attracted tremendous research interest, since they are expected to achieve battery‐level energy density, while having a long calendar life and short charging time. Herein, a novel asymmetric supercapacitor has been successfully assembled from NiCo2S4 nanosheets and spinous Fe2O3 nanowire modified hollow melamine foam decorated with polypyrrole as positive and negative electrodes, respectively. Owing to the well‐designed nanostructure and suitable matching of electrode materials, the assembled asymmetric supercapacitor (ASC) exhibits an extended operation voltage window of 1.6 V with an energy density of 20.1 Wh kg−1 at a power density of 159.4 kW kg−1. Moreover, the ASC shows stable cycling stability, with 81.3 % retention after 4000 cycles and a low internal resistance of 1.03 Ω. Additionally, a 2.5 V light‐emitting diode indicator can be lit up by three ASCs connected in series; this provides evidence of the practical application potential of the assembled energy‐storage system. The excellent electrochemical performances should be credited to the significant enhancement of the specific surface area, charge transport, and mechanical stability resulting from the unique 3D morphology. [ABSTRACT FROM AUTHOR]

MXenes are a new family of 2 D transition metal carbides and nitrides, which have attracted enormous attention in electrochemical energy storage, sensing technology, and catalysis owing to their good conductivity, high specific surface area, and excellent electrochemical properties. In this work, a series of Co3O4‐doped 3 D MXene/RGO hybrid porous aerogels is designed and prepared through a facile in situ reduction and thermal annealing process, in which the reduced graphene oxide (RGO) conductive network can electrically link the separated Co3O4‐MXene composite nanosheets, leading to enhanced electronic conductivity. It is found that upon using the Co3O4‐MXene/RGO hybrid porous aerogel prepared with a mass ratio of Co3O4‐MXene/RGO of 3:1 (CMR31) as an electrode for a supercapacitor, a superior specific capacitance of 345 F g−1 at the current density of 1 A g−1 is achieved, which is significantly higher than those of Ti3C2Tx MXene, RGO, and MXene/RGO electrodes. In addition, a high capacitance retention (85 % of the initial capacitance after 10 000 cycles at a high current density of 3 A g−1) and a low internal resistance Rs (0.44 Ω) can be achieved. An all‐solid‐state asymmetric supercapacitor (ASC) device is assembled using CMR31, and it has the ability to light up a blue LED indicator for 5 min if four ASCs are connected in series. Therefore, these novel Co3O4‐MXene/RGO hybrid porous aerogels have potential practical applications in high‐energy storage devices. Porous aerogel electrodes: A Co3O4‐doped 3 D MXene/RGO hybrid porous aerogel (see figure) was synthesized through a facile in situ reduction and thermal annealing process. It shows excellent potential for use in high‐performance all‐solid‐state asymmetric supercapacitors. [ABSTRACT FROM AUTHOR]

Composite of CoS 1.97 nanoparticles decorated CuS hollow cubes and reduced graphene oxide (rGO) (CCSrGO) thin film flexible positive electrode is fabricated as the anode material of supercapacitor with broad application prospects in electrochemical energy storage. [Display omitted] Stretchable flexible thin-film electrodes are extensively explored for developing new wearable energy storage devices. However, traditional carbon-based materials used in such independent electrodes have limited practical applications owing to their low energy storage capacity and energy density. To address this, a unique structure and remarkable mechanical stability thin-film flexible positive electrode comprising CoS 1.97 nanoparticles decorated hollow CuS cubes and reduced graphene oxide (rGO), hereinafter referred to as CCSrGO, is prepared. Transition metal sulfide CoS 1.97 and CuS shows high energy density owing to the synergistic effects of its active components. The electrode can simultaneously meet the high-energy density and safety requirements of new wearable energy storage devices. The electrode has excellent electrochemical performance (1380 F/g at 1 A/g) and ideal capacitance retention (93.8 % after 10,000 cycles) owing to its unique three-dimensional hollow structure and polymetallic synergies between copper and cobalt elements, which are attributed to their different energy storage mechanisms. Furthermore, a flexible asymmetric supercapacitor (FASC) was constructed using CCSrGO as the positive electrode and rGO as the negative electrode (CCSrGO//rGO), which delivers an energy density of 100 Wh kg−1 and a corresponding power density of 2663 W kg−1 within a voltage window of 0–1.5 V. The resulting FASC can power a light-emitting diode (LED) at different bending and twisting angles, exerting little effect on the capacitance. Therefore, the prepared CCSrGO//rGO FASC devices show great application prospects in energy storage. [ABSTRACT FROM AUTHOR]

The synergic effect of multi-bonding interactions (including hydrogen bonding, covalent bonding and electrostatic interactions) are achieved by pre-polymerised polydopamine and polyethyleneimine cross-linked MXene layers (p-DEM).The resulting MXene composite films exhibit good electrical conductivity, mechanical strength, and energy storage capability. Given these superior attributes, the flexible supercapacitor devices based on these films demonstrate stable energy storage performances under different bending tests. [Display omitted] Demands for high-strength flexible electrodes have significantly increased across various fields, especially in wearable electronics. Inspired by the strong integrated layered structure of the natural nacre via multi-bonding interactions, we report the fabrication of the strong integrated nacre-like composite films based on pre-polymerised polydopamine and polyethyleneimine cross-linked MXene layers (p-DEM), achieving the synergic effect of hydrogen bonding, covalent bonding and electrostatic interactions. As a result, a high-level tensile strength of ∼302 MPa, 10.8 times higher than that of the plain MXene film, is obtained for the prepared p-DE 0.5 M composite film. Meanwhile, the composite film also delivers superior energy storage (∼1218F cm−3 at 5 mV s−1) and rate performances (capacitance retention of 81.3% at 1000 mV s−1). To demonstrate the practical application of the composite films, a symmetrical supercapacitor based on p-DE 0.5 M electrodes is assembled, which shows stable energy storage performances under different deformation states such as bending angles at 0, 60, 90 and 180°, or withstand repeated bending times (1000 cycles). This type of multi-bonding interactions induced strong integrated MXene assembly may promote the wide applications of MXene-based films in flexible electronics, artificial intelligence, and tissue engineering, to name a few. [ABSTRACT FROM AUTHOR]

[Display omitted] • The NCO/MGA-300 has excellent elastic properties and compressive durability. • DFT calculations prove that NCO/MGA-300 has better electrochemical performance. • The NCO/MGA-300 has superb specific capacitance, rate performance and stability. • The aNCMSC shows stable electrical properties after 100 compression-release cycles. Compression-tolerant electrodes are critical for developing next-generation wearable energy storage devices. However, most of previous studies on compressible electrodes focus on carbon-based materials, whereas metal-based materials such as spinel metal oxide with faradaic nature have been rarely studied due to their lack of compressibility. Herein, NiCo 2 O 4 (NCO) microtubes assembled by ultrathin and mesoporous nanosheets, are deposited on/into Ti 3 C 2 T x MXene/reduced graphene oxide aerogel (MGA), an intrinsically compressible host template with high conductivity and specific surface areas. The optimized NCO/MGA-300 sample shows a reversible compressive strain of 60% and a superior durability. Density functional theory (DFT) calculations reveal that the NCO/MGA-300 heterojunction has high electronic conductivity, fast electron transfer ability, and low adsorption energy for OH– ions. As a result, the NCO/MGA-300 electrode exhibits superb electrochemical performance in terms of its high gravimetric capacitance (1633F g−1 at 1 A g−1), rate performance (1492F g−1 at 10 A g−1), and remarkable cycling stability of 86.6% after 10,000 charge-discharging cycles. Moreover, an assembled asymmetric supercapacitor based on compressible NCO/MGA-300 shows stable electrochemical performances under different compressive strains (20%. 40% and 60%), or after 100 compression-release cycles. This research finding demonstrates the possibility of metal-based electrode for wearable devices with high energy storage capability and good compressibility. [ABSTRACT FROM AUTHOR]

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]

[Display omitted] • Co 3 Se 4 quantum dot electrode material coated with N doped porous nanocarbon is prepared. • The assembled all-solid-state ASC attenuate only 4.4% of C s after 15,000 GCD cycles. • The assembled all-solid-state ASC has an energy density of 84.59 Wh kg−1 at a power density of 799.99 W kg−1. Transition metal selenides (TMSe) are considered as potential anode materials for supercapacitors because of their abundant reserves and high safety. However, their poor conductivity limits their high rate performance and stability. In this paper, an N -doped porous nanocarbon-coated Co 3 Se 4 quantum dots (NCCS-QDs) composite is prepared as the cathode material of supercapacitor. The formation of Co 3 Se 4 quantum dots complies with a size minimization strategy to speed up ion transport. At the same time, the Co 0.85 Se nanosheets are converted into Co 3 Se 4 quantum dots, avoiding the collapse of the nanosheets during the electrochemical process. In addition, the porous nanocarbon coating increases the number of active sites and the contact area between the electrode and the electrolyte, which can provide more ion transport channels and pore sizes, while avoiding the generation of inactive clusters in the electrochemical reaction of quantum dots. The as-assembled NCCS-QDs-2//AC ASCs devices demonstrate excellent electrochemical performance with an energy density of 84.59 Wh kg−1 at a power density of 799.99 W kg−1. At the same time, the ASCs device showed excellent cycle stability, with 95.6% of the initial capacitance still maintained after 15,000 charge and discharge cycles. The excellent electrochemical performance of NCCS-QDs-2//AC ASC device proves that NCCS-QDs composite material has a broad application prospect in the cathode material of supercapacitor. [ABSTRACT FROM AUTHOR]

The planning and synthesis of nanocomposite materials with reasonable core-shell heterostructure are of great significance in enhancing the energy density, structural stability as well as long cycle life of asymmetric supercapacitors. We have successfully prepared CuCo 2 O 4 @CuCo 2 S 4 @Ni(OH) 2 core-shell 3D nanoflower array electrode material, resulting in outstanding performance of the assembled supercapacitor. Firstly, CuCo 2 O 4 (CuC) nanowires are grown directly on nickel foam (NF) through hydrothermal and calcination reactions, followed by the formation of heterogeneous CuCo 2 O 4 @CuCo 2 S 4 (CuC@CuS) nanoflowers via a hydrothermal reaction by using Na 2 S·9H 2 O as a vulcanizing agent. Finally, CuCo 2 O 4 @CuCo 2 S 4 @Ni(OH) 2 electrode material is obtained via the electrodeposition method under a constant voltage. The prepared electrode material is composed of conductive CuC@CuS nanoflowers as the core and deposited Ni(OH) 2 nanosheets as the shell, which effectively promotes ion diffusion, increases the reactive area and thereby enhances the electrochemical performance. Impressively, the composite electrode CuC@CuS@Ni(OH) 2 /NF material achieves an exciting high capacitance of 3753.6 F g−1 (1 A g−1), and the cycle stability is reduced by only 7.1 % after 10,000 cycle tests in the standard three-electrode system. Furthermore, the asymmetric supercapacitor (ASC) device composed of activated carbon (AC) and CuC@CuS@Ni(OH) 2 exhibits 729.75 W kg−1 power density under 59.11 Wh kg−1 energy density. The aforementioned findings demonstrate that the CuC@CuS@Ni(OH) 2 nanoflower array is a very potential energy storage material. The flower-shaped CuC@CuS@Ni(OH) 2 /NF composite with core-shell structure is constructed via facile hydrothermal and annealing processes followed by electrodeposition. [Display omitted] [ABSTRACT FROM AUTHOR]

The voltage limit of water-based asymmetric supercapacitors is usually 2 V, which prevents further improvement of energy density. Na 0.6 CoO 2 nanoarrays with high Na content are formed on carbon cloth (CC) by cyclic electrochemical oxidation (EO) and can work stably in 0–1.2 V wide potential, and the specific capacitance is up to 575.98C g−1 at 1 A g−1. Using carbon coated Fe 2 O 3 nanoarrays on CC as the negative electrode and Na 0.6 CoO 2 /CC as the positive electrode, a water-based asymmetric supercapacitor (ASC) which can operate stably in 0–2.5 V wide voltage window is assembled. The Na 0.6 CoO 2 /CC//Fe 2 O 3 @C/CC ASC exhibits an energy density of 133.92 Wh kg−1 at a power density of 1250 W kg−1, which is better than previously reported Co-based supercapacitors. This study provides a scheme for the working voltage of water-based ASCs to be further expanded to more than 2 V. Utilizing cationic pre-inserted Co 3 O 4 nanoarray to construct high operating voltage composite electrode should have broad application prospect. [Display omitted] • Na 0.6 CoO 2 nanosheets with high Na content are prepared by electrochemical oxidation. • The prepared Na 0.6 CoO 2 /CC electrode can work stably at a wide potential range of 0–1.2 V. • The Na 0.6 CoO 2 /CC//Fe 2 O 3 @C/CC ASC device can operate stably at 0–2.5 V wide potential range. [ABSTRACT FROM AUTHOR]

The flower-shaped CuC@CuS@CH-15 composite with core–shell structure is constructed via facile hydrothermal and annealing processes followed by electrodeposition method and exhibits excellent electrochemical performance. [Display omitted] • CuC@CuS@CH-15 with core–shell structure is successfully grown on NF. • The electrode with a flower structure provides a large surface area for redox reaction. • 1D and 2D materials are utilized to construct 3D materials by chemical reactions. • CuC@CuS@CH-15//AC ASC delivers high energy and power densities. • The CuC@CuS@CH-15 can be utilized as bind-free electrode for SCs. Here, we prepare three-dimensional nanoflower-shaped CuCo 2 O 4 @CuCo 2 S 4 @Co(OH) 2 core–shell materials on nickel foam (NF). CuCo 2 O 4 (CuC) nanowire arrays and CuCo 2 S 4 (CuS) nanosheets are grown directly on NF as the core through routine hydrothermal and high-temperature calcination methods and Co(OH) 2 (CH) small nanosheets deposited on CuC@CuS nanoflowers via the potentiostatic deposition for 15 mins. Due to its distinctive structure and the synergistic effect between multiple components of CuCo 2 O 4 @CuCo 2 S 4 @Co(OH) 2 , the electrode has a fantastic specific capacitance (C s , 4075F/g) under the current density of 1 A/g and satisfying cyclic stability (88.4 % capacitance retention and 84.6 % coulomb efficiency after 10,000 cycles). Additionally, an asymmetric supercapacitor (ASC) device equipped with CuC@CuS@CH-15/NF as a positive and active carbon (AC) electrode as a negative electrode can work steadily at 0–1.6 V. The ASC device can offer an excellent energy density (E, Wh kg−1) of 232.02 Wh kg−1 at a high-power density of 2879.8 W kg−1 (P, W kg−1) and an unexpected cycle stability (84.2 % of the original C s and 81.7 % of coulombic efficiency after 10,000 repeated GCD tests), which far surpasses other ASCs of the same type. These results guide to enhancement of the electrochemical properties of cobalt-based oxides/sulfides@Co(OH) 2 as the positive electrode for supercapacitors. [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]

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]

[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]

• The sample were designed and prepared through the facile hydrothermal process. • The NiFe-LDH@CoS 2 @Ni electrode exhibits a high capacity of 11.28 F cm-2 (3880 F g-1) at a current density of 2 mA cm-2 (1.17 A g-1). • When the NiFe-LDH@CoS 2 @Ni fabricated as an ASC device, it can light up a blue LED for 30 min. Layered double hydroxides (LDHs) are a kind of classic pseudocapacitive materials with lamellar structure and large specific surface area, which have attracted swinging attention in the electrochemical energy storage area. The CoS 2 @Ni is synthesized through a hydrothermal process, followed by surface generation of the flower-like nickel-iron layered double hydroxide (NiFe-LDH) nanospheres through a hydrothermal process, which is directly used to design a binder-free electrode with a splendid capacitance capability. The as-synthesized NiFe-LDH@CoS 2 @Ni electrode presents an outstanding specific capacitance of 11.28 F cm−2 (3880 F g−1) at 2 mA cm−2 (1.17 A g−1) in a three electrodes system. Also, the all-solid-state asymmetric supercapacitor (ASC) is combined utilizing the NiFe-LDH@CoS 2 @Ni hybrid as the positive electrodes and active carbon covered Ni foam as negative electrodes, respectively. The as-fabricated ASC exhibits a high energy density of 15.84 Wh kg−1 at the power density of 375.16 W kg−1 and can be able to lighten a blue LED indicator for more than 30 min, revealing that the prepared NiFe-LDH@CoS 2 @Ni owns great potential in the aspect of practical applications. Therefore, the prepared NiFe-LDH@CoS 2 @Ni with outstanding electrochemical properties could be applied for high-performance supercapacitors. [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]

A fiber asymmetric supercapacitor system is designed with NiCo-LDH nanoflakes and FeOOH nanosheets anchored on electrochemically activated graphite fibers as positive electrode and negative electrode, respectively. Due to the formation of C O Metal bonding, the oxygen-functionalized carbon on electrochemically activated graphite fibers can bind strongly with NiCo-LDH and FeOOH, which assists in establishing the fast electron transfer routes and fluent ion transport avenues. Both NiCo-LDH and FeOOH anchored on electrochemically activated graphite fibers display a high rate performance, 80% and 87.3% of the electric capacity can be reserved with the current density increasing from 2 to 20 A g−1 and 2 to 10 A g−1, respectively, while the NiCo-LDH and FeOOH deposited on untreated graphite fibers can only retain 45% and 40%. The fabricated novel solid-state fiber asymmetric supercapacitor device exhibits an expanded operation potential window of 1.8 V with a maximum energy density (130 W h kg−1) when the power density is 1.8 kW kg−1. Furthermore, a high energy density (81 W h kg−1) is still achieved at a superhigh power density (10.8 kW kg−1). Additionally, a good cycling stability of the solid-state fiber asymmetric supercapacitor can be obtained (90% capacity retention after 10,000 cycles). [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]

• MOFs were utilized as templates to obtain porous nanostructure. • Electrochemical activation endowed CC with excellent hydrophilic property. • Unique hydrolysis and ion exchange/etching method was used in this work. • The hybrid supercapacitor exhibited excellent flexibility and wearability. Flexible electrodes with favorable architectures are urgently demanded for flexible and wearable supercapacitors with high performance. Herein, we demonstrate the rational design and preparation of hollow and ultrathin nickel cobalt sulfides nanosheets arrays on electrochemical activated carbon cloth (Ni-Co-S/ACC) for fabrication of flexible hybrid supercapacitors, where the Ni-Co-S nanosheets are derived from the metal-organic framework via an etching/ion exchange method. The Ni-Co-S/ACC electrode can deliver a very high specific capacitance of 2392 F/g at the current density of 1 A/g and good rate performance (80.3% capacitance retention at 20 A/g). The enhanced electrochemical properties should be attributed to the hydrophilic property, good conductivity and enriched redox active sites resulted from the electrochemical activated carbon cloth and the hollow and ultrathin structure of Ni-Co-S nanosheets. When a flexible hybrid supercapacitor is assembled using Ni-Co-S/ACC as positive electrode and activated carbon as negative electrode, it shows high energy density of 30.1 Wh/Kg at power density of 800.2 W/Kg as well as predominant cycling stability (82% retention after 10,000 cycles). Furthermore, the excellent flexibility and wearability of the hybrid supercapacitor could envision promising applications in high-performance wearable energy storage devices. [ABSTRACT FROM AUTHOR]

DFT calculation is used to study the electrochemical capacity enhancement mechanism of the fabricated flexible 3D porous rOHNM-AGs electrodes based on open-hollow Ni-MOF microspheres with high mechanical strength and superior electrochemical properties. [Display omitted] • 3D rOHNM-AGs are achieved by embedding open-hollow Ni-MOF microspheres into graphene nanosheets. • DFT calculation reveals charge-transfer interaction between the rOHNM-AGs and OH– ions. • The rOHNM-AGs/KOH/PVA film can be twisted with different angles, which can lift 500 g plastic bottle. • The fabricated rOHNM-AGs electrode exhibit superb specific capacitance of 1644F·g−1 at 1 A·g−1. • A portable multifunctional instrument can be powered by all-solid-state supercapacitor device for 15 mins. Metal-organic frameworks (MOFs) are extensively used for electrode materials of supercapacitors under their unique characteristics like customizable pore size, plentiful active sites and tunable structure. However, the MOFs lack adequate electrical conductivity and satisfactory stability, when directly applied to supercapacitor electrode materials, limiting the further improvement of their electrochemical properties. Accordingly, three-dimensional porous aerogels (rOHNM-AGs) have been achieved by embedding open-hollow nickel-based metal–organic framework microspheres between graphene layers. Under the controllable and highly ordered metal nodes as well as organic linkers, the prepared rOHNM-AGs still reserve the preponderance of MOF materials with multifarious exceptional constituent and configurational benefits. Furthermore, the remarkable electrical conductivity from graphene leads to a significant increase in electron/ion transport rate. In addition, charge-transfer interaction between the acceptor of OH– ions and the donor of rOHNM-AGs has been exposed by the density functional theory calculations. Moreover, a pliable and high tensile rOHNM-AGs/PVA/KOH film electrode has been fabricated by the PVA/KOH gel-electrolyte, which is capable of curving at multifarious angles. For actual utilizations, the manufactured supercapacitor apparatus can run a multi-purpose display for over 15 mins. Therefore, this groundbreaking research furnishes a new inspiration for preparing composite electrodes based on MOFs and graphene for flexible asymmetric supercapacitors. [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]

Graphical abstract Highlights • Thermally-treated and acid-etched method is utilized to obtain flexible carbon fiber cloth. • N/O-enriched carbon fibers exhibit high surface area and large pore volume. • N- and O-rich functional groups can generate high pseudocapacitance. • The electrode based on N/O-enriched carbon fibers cloth shows prominent area-capacitance and flexibility. Abstract The fast development of portable devices has greatly stimulated the demand for flexible supercapacitors (FSCs). The key to assembling FSCs lies in the development of electrodes with high-performance and good flexibility. In this work, oxygeneous groups modified nitrogen-doped carbon fibers cloth (ONCC) was obtained through annealing the pre-oxidized polyacrylonitrile cloth (PPC), followed by a facile oxidation process using a mixture of concentrated sulfuric acid and concentrated nitric acid. By changing annealing temperature, the nitrogen content can be controlled in the obtained ONCC. It was found that the PPC annealed at 950 °C followed by acid etching for 60 min could deliver the excellent areal and gravimetric specific capacitance of 1385 mF cm−2 and 294.7 F g−1 at the current density of 1 mA cm−2, outstanding rate performance and superb cycling stability. Furthermore, the assembled FSC delivered a high energy density of 19.8 μWh cm−2 (4.03 Wh kg−1) at a power density of 50.1 μW cm−2 (10.2 W kg−1) and good flexibility under different bending conditions. This work provides a facile and efficient route to prepare high-performance carbon fiber based electrode materials in large scale for flexible all-solid-state energy storage devices. [ABSTRACT FROM AUTHOR]

Abstract The introduction of surface functional groups onto graphite can provide additional pseudocapacitance for supercapacitors. However, the compensation for the loss of electrical conductivity arising from the destruction of the π-π conjugation remains a big challenge. Here, the graphite paper is electrochemically oxidized first, followed by the mild reduction using hydroiodic acid to afford the largely exfoliated and moderately reduced sample (noted as MOGP-4). The as-prepared MOGP-4 not only has the abundant oxygenous groups, but also preserves the highly conductive network (sp2 carbon). Owing to the good conductivity (1.14 × 103 S m−1), MOGP-4 exhibits a high rate capability of 93% (from 18.3 mF cm−2 to 17 mF cm−2) as the current density increases from 0.5 to 10 mA cm−2 and predominant cycling performance. Furthermore, the flexible solid-state supercapacitors (SSCs) based on MOGP-4 with different sizes are assembled and deliver excellent durability, high flexibility and superior rate capability. The high electrochemical performances of the as-fabricated supercapacitors should envision promising applications for energy storage devices. Graphical abstract Image 1 highlights Graphite paper (GP) row material is low-cost, commercial, large-area and flexible. GP is electrochemically oxidized in mixed acids and then mildly reduced by HI. The strategy can introduce oxygenous groups and preserve high conductivity of GP. The fabricated SCs have high rate capability, stability and coulombic efficiency. [ABSTRACT FROM AUTHOR]

Supercapacitors are attracting increasing research interest because they are expected to achieve battery-level energy density while having a long calendar life and a short charging time. However, the development of large-scale and cost-reasonable production methods for flexible, wearable and arbitrary-shaped supercapacitor devices still faces enormous challenges. Herein, a 3D-network, porous graphene/CoS 2 /Ni 3 S 4 (G/CoS 2 /Ni 3 S 4) composite electrode has been designed and synthesized through a combination of solvothermal and vulcanization methods. By combining the networked CoS 2 /Ni 3 S 4 nanoflakes with reduced graphene oxide (RGO) nanosheets, the as-prepared composite electrode exhibits good conductivity, a high density of electrochemically active sites and good cycling stability. The result is a high specific capacitance of 1739 F g−1 at a current density of 0.5 A g−1. Significantly, the arbitrary-shaped G/CoS 2 /Ni 3 S 4 ||GF hybrid supercapacitor devices can be printed directly on different substrates, which favorably combine mechanical flexibility, good cycling performance and high energy density. This methodology may be feasible to prepare fully-printable and wearable supercapacitors, and other electronic devices in large scale, thereby holding enormous potential for wearable technologies. Image 1 [ABSTRACT FROM AUTHOR]

Herein, we report the preparation of strongly coupled nickel boride/reduced graphene oxide (Ni 2 B/RGO) hybrid via simultaneous chemical reduction of nickel dichloride (NiCl 2 ·6H 2 O) and graphene oxide (GO) in one pot using NaBH 4 as reductant under nitrogen atmosphere. The Ni 2 B/RGO hybrid is demonstrated to be an excellent and novel electrode material for supercapacitors. The specific capacitance of Ni 2 B/RGO hybrid annealed at an optimized temperature of 200 °C (Ni 2 B/RGO-200) can reach 1073.4 F g −1 at a current density of 1 A g −1 in 6 M KOH solution. Meanwhile, the hybrid supercapacitor (HSC) device fabricated using Ni 2 B/RGO-200 as positive electrode and activated carbon (AC) as negative electrode delivers a high energy density of 22.1 Wh kg −1 at a power density of 724.9 W kg −1 . After 2500 charge-discharge cycles at a current density of 6 A g −1 , the HSC can still retain 72.4% of its initial performance. The excellent capacitor performance of Ni 2 B/RGO-200 hybrid should not only attribute to the adequate electrochemical reaction active sites of Ni 2 B particles, but also the enhanced electron transfer rate and superior electrochemical stability of graphene. [ABSTRACT FROM AUTHOR]

The MC@ZnCo-LDH-2/NF composite with honey-comb structure was constructed via hydrothermal and electrodeposition methods and exhibits excellent pseudocapacitance and cyclic stability. [Display omitted] • MgCo 2 O 4 @ZnCo-LDH with honeycomb shape is successfully grown on NF substrate. • MgCo 2 O 4 @ZnCo-LDH with large surface area provides sufficient redox-active sites. • The crosslinked network electrode exhibits enhanced electrochemical performance. • The MgCo 2 O 4 @ZnCo-LDH//AC ASC delivers a high energy and power density. MgCo 2 O 4 (MC) is a ternary transition metal oxide that has attracted much attention owing to its superb electrochemical properties. Whereas, the sole MC electrode material is difficult to achieve its theoretical specific capacitance (C s) in practical applications owing to its simple structure, low specific surface area and poor cycle stability. In this study, the assembled MC@ZnCo-LDH on nickel foam (NF) with honeycomb-like microstructure materials by a simple hydrothermal method, calcination treatments and electrodeposition methods. At a current density of 1 A g−1, the C s of the as-prepared MC@ZnCo-LDH/NF electrode material can reach 2353.8F/g, which is higher than that of MC/NF or ZnCo-LDH/NF related electrode materials. Moreover, an asymmetric supercapacitor (ASC) is successfully assembled with MC@ZnCo-LDH/NF as positive electrode and active carbon (AC) as negative electrode. The MC@ZnCo-LDH/NF//AC device exhibits a relatively high energy density of 61.64 Wh kg−1 at a power density of 750 W kg−1 and it can still maintain 88.9 % of the original specific capacitance after 10,000 cycles. A heart-like LED indicator can be lit by three all-solid asymmetric supercapacitors connected in series for 12.5 mins. The design of honeycomb-like MC@ZnCo-LDH materials may open up a methodology for next-generation high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Exploiting earth-abundant and cost-efficient electrode materials is an effective strategy to fulfil the urgent demand for high-efficiency energy-storage. Carbon aerogels (CAs) with conductive skeleton and large specific area have attracted significant attention in electrode materials. However, how to achieve the large-scale production of CAs with both high energy storage capability and reasonable cost still remains a challenge. Herein, a scalable and cost-effective route toward constructing cobalt sulfide nanoparticles/carbon aerogel (CoS 1.97 /CA) hybrid electrode is described. Quantum-sized CoS 1.97 nanoparticles are synthesized by in situ selective vulcanization of Co2+ absorbed on the carbonaceous watermelon tissues which acts as current collector for the fast electrons transfer. Quantum-sized CoS 1.97 nanoparticles provide abundant active sites for the redox reaction with electrolyte ions in the hybrid electrode, thus leading to an excellent electrochemical capacity of 1715 C g−1. Furthermore, an asymmetric supercapacitor is assembled by employing CoS 1.97 /CA-500 as positive electrode and CA as negative electrode, which delivers the highest capacity of 51.5 mAh g−1 and energy density of 36.4 Wh kg−1. In addition, an impressive cycling span of 20000 cycles is obtained with capacity retention reaching up to 98.9%, demonstrating its high stability for real-world application. These findings demonstrate the bio-inspired and cost-effective development of 3D carbon aerogel electrode for incorporating with other novel materials for the applications in energy storage. [Display omitted] • Scalable and cost-effective strategy was developed for synthesizing biomass carbon aerogel (CA). • The aerogel provides stable transport and abundant active sites for both electrons and electrolyte ions. • Quantum-sized CoS 1.97 -NPs are synthesized by in situ vulcanization process on CA skeleton. • The resulting CoS 1.97 /CA-500 electrode possesses both high energy storage capability and cycling stability. [ABSTRACT FROM AUTHOR]

• Ti 3 C 2 T x MXene based foam (MGC) is fabricated through a template method. • Interconnected MXene/rGO network renders the foam with good compressibility. • The MGC/PVA-H 2 SO 4 composite foam can be compressed into flexible film. • The assembled supercapacitor devices show good reliability under varied deformation states. Free-standing electrodes with high electrical conductivity, good deformability and durability are critical for flexible electronics, especially in field of wearable energy storage devices. Here, three dimensional (3D) Ti 3 C 2 T x MXene/reduced graphene oxide (rGO)/carbon (MGC-500) hybrid electrode fabricated by the simple template method is presented. Commercial melamine foam (MF) worked as template not only enables the Ti 3 C 2 T x /rGO nanosheets to form a porous architecture, but also introduces the heteroatom nitrogen into the Ti 3 C 2 T x /rGO nanosheets during the annealing process. The as-prepared MGC-500 electrode shows a gravimetric capacitance of 276F g−1 at a current density of 0.5 A g−1. When the MGC-500 hybrid electrodes are assembled into an all solid-state supercapacitor, it shows a stable electrochemical performance at different compressive strains. Notably, we find that the MGC-500 foam electrode coated with PVA-H 2 SO 4 gel electrolyte can be compressed into flexible film at 80% of compression. And the supercapacitor devices assembled by the film also exhibit stable capacitance under different modes of deformations such as bending and twist. The developed template approach offers a simple strategy to fabricate free-standing Ti 3 C 2 T x MXene electrode for energy storage devices that can withstand varied deformations, and also can be extended to other members of the large MXene family. [ABSTRACT FROM AUTHOR]

[Display omitted] • MgCo 2 O 4 @α-Co(OH) 2 core–shell nanoarrays is fabricated on Ni foams. • The materials are obtained by a facile hydrothermal strategy. • MgCo 2 O 4 @α-Co(OH) 2 electrode exhibits superb supercapacitive performance. In this work, the MgCo 2 O 4 @α-Co(OH) 2 core–shell structure (MgCo 2 O 4 @α-Co(OH) 2 /NF) on foam nickel was prepared using hydrothermal annealing and chemical bath deposition processes to form a supercapacitor positive electrode. MgCo 2 O 4 @α-Co(OH) 2 /NF-2 composite material, with a deposition time of 20 min in a chemical bath, showed a specific capacitance of 1634.8 F g−1 at 1 A g−1, a long cycle stability of 89.4% (in 10,000 cycles) and a rate performance of 78.29%, with excellent electrochemical impedance performance (Rs ≈ 0.507 Ω). The MgCo 2 O 4 @α-Co(OH) 2 /NF-2//AC asymmetric supercapacitors (ASCs) showed a specific capacitance of 185.46 F g−1 at 1 A g−1, with a good long-cycle stability of 91.7% preservation rate after 10,000 cycles. At a power density of 773.19 W kg−1, the energy density is high (65.94 Wh kg−1). We demonstrated that three prepared ASCs devices can produce a diode with a rated voltage of 3 V that continues to emit light for 10 min. This study shows that the MgCo 2 O 4 @α-Co(OH) 2 /NF-2 electrode can be used as a positive electrode for high-efficiency energy storage devices. [ABSTRACT FROM AUTHOR]

Freestanding electrodes fabricated with hierarchical core-shell micro-/nano-structured materials synthesized from redox-type metal oxides show enormous potential for portable electronic devices. In this, a novel and facile strategy for the preparation of petaloid and origami-lantern shaped MnO 2 /Co 2 CH@C hierarchical porous core-shell nanorod arrays is proposed. The fabricated electrode based on MnO 2 /Co 2 CH@C hybrid composite exhibits superior capability of 2022 mF cm−2 under high current density of 5 mA cm−2, which can be explained by the well-oriented petal-like and origami-lantern shaped nanosheets as well as the 3D core-shell porous hierarchical structure. Additionally, a solid-state asymmetric supercapacitor equipment is assembled on basis of the synthesized hierarchical MnO 2 /Co 2 CH@C hybrid, exhibiting an energy density of 15 Wh kg−1 at the power density of 255 W kg−1. Notably, the multifunctional instrument can be operated by the assembled device for 8 min, while monitoring time, temperature and air humidity in a portable outdoor environment. Moreover, a blue indicator can also be operated for 9 min long, evidencing their potential commercial applications. Overall, this work demonstrates the promising potential of the synthesized novel origami-lantern shaped and highly oriented hierarchical composites for electrochemical energy storage applications. Petaloid and origami-lantern shaped MnO 2 /Co 2 CH@C hierarchical core-shell nanorod arrays are synthesized and employed for portable asymmetric supercapacitor. [Display omitted] • Petaloid and origami-lantern shaped MnO 2 /Co 2 CH@C hybrid is synthesized. • The fabricated MnO 2 /Co 2 CH@C electrode exhibits great electrochemical properties. • Multifunctional instrument and LED indicator can be powered for 8 min. • The instrument can monitor time, temperature and air humidity in outdoors. [ABSTRACT FROM AUTHOR]

A hierarchical structure electrode material composed of MgCo 2 O 4 nanowire loaded NiCo-LDH nanosheets shows excellent capacitance and stability and superb energy density. Impressively, two MgCo 2 O 4 @NiCo-LDH/NF-2//AC asymmetric supercapacitor devices connected in series can light up the LED indicators for up to 15 min, showing a broad practical application prospect. • MgCo 2 O 4 @NiCo layered double hydroxide (LDH) hierarchical structure nanocomposites is fabricated on 3D Ni foams. • The materials are obtained by a facile hydrothermal strategy. • MgCo 2 O 4 @NiCo-LDH electrode exhibits superb supercapacitive performance. In this work, MgCo 2 O 4 @NiCo layered double hydroxide (LDH) hierarchical structure 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 @NiCo-LDH/NF hierarchical structure nanocomposites via the second hydrothermal process. It is found that the MgCo 2 O 4 @NiCo-LDH/NF nanocomposite prepared from 9 h hydrothermal reaction (MC@NC-LDH-2) exhibits an excellent specific capacitance of 5701.2 F g−1 at the current density of 1 A g−1. Moreover, a high capacitance retention (83.7% maintained after 5000 cycles) and a low internal resistance (Rs) (0.783 Ω) can be achieved. Furthermore, a quasi-solid state asymmetric supercapacitor (ASC) is assembled using MgCo 2 O 4 @NiCo-LDH/NF-2 as positive electrode and activated carbon (AC) as negative electrode. The as-fabricated MgCo 2 O 4 @NiCo-LDH/NF-2//AC ASC shows a high energy density of 89.79 Wh kg−1 at 800 W kg−1. Meanwhile, the MgCo 2 O 4 @NiCo-LDH/NF-2//AC ASC device possesses an excellent cycling stability of 89.03% retention of the initial capacitance after 5000 cycles and two ASC devices connected in series can light up a LED bulb for 15 min. Our results manifest that these hierarchical MgCo 2 O 4 @NiCo-LDH composites could envision huge potential application in energy storage devices. [ABSTRACT FROM AUTHOR]

In this work, hierarchical MgCo 2 O 4 @CoFe layered double hydroxide (LDH) core-shell nanowire arrays on Ni foam (NF) are synthesized by facile hydrothermal and calcination methods. MgCo 2 O 4 /NF has been first synthesized via a hydrothermal reaction and annealing treatment and then utilized to prepare MgCo 2 O 4 @CoFe-LDH/NF core-shell nanocomposites via the second hydrothermal reaction. It is found that the MgCo 2 O 4 @CoFe-LDH/NF core-shell nanocomposite prepared from 3 h hydrothermal reaction (MC@CF-LDH-3) exhibits an excellent specific capacitance of 903.15 C g−1 (2007 F g−1) at the current density of 1 A g−1. Moreover, a high capacitance retention (80.2% maintained after 5000 cycles) and a low internal resistance (Rs) (0.75 Ω) can be acquired. Furthermore, an all-solid-state asymmetric supercapacitor (ASC) is assembled using MgCo 2 O 4 @CoFe-LDH/NF-3 as the positive electrode and activated carbon (AC) as the negative electrode. The as-fabricated MgCo 2 O 4 @CoFe-LDH/NF-3//AC ASC shows a high energy density of 60.82 Wh kg−1 at 725 W kg−1. Meanwhile, the MgCo 2 O 4 @CoFe-LDH/NF-3//AC ASC device possesses an excellent cycling stability of 93.6% retention of the initial capacitance after 5000 cycles and two ASC devices connected in series can light up a LED bulb for 8 min. Our results manifest that this hierarchical MgCo 2 O 4 @CoFe-LDH composite has huge potential application in energy storage devices. Image 1 • MgCo 2 O 4 @CoFe-LDH core-shell nanoarrays is fabricated on Ni foams. • The materials are obtained by a facile hydrothermal strategy. • MgCo 2 O 4 @CoFe-LDH electrode exhibits superb supercapacitive performance. [ABSTRACT FROM AUTHOR]

Here we report the construction of a kind of electrode material with excellent capacitive performance composed of Ni, Co and Al layered double hydroxide (NiCoAl-LDH) nanosheets branched on Cu 2+1 O nanorod arrays (Cu 2+1 O@NiCoAl-LDH) on copper foam current collector, which is obtained via an easy in situ chemical oxidation reaction in combination with hydrothermal method. The as-prepared Cu 2+1 O@NiCoAl-LDH electrode presents observably enhanced electrochemical performance with an outstanding specific capacitance (2932 F g−1 at 0.75 A g−1), and extraordinary cycling stability (94.27% of the initial capacitance maintained after GCD test for 6000 cycles), which are much superior to those of Cu(OH) 2 and Cu 2+1 O@NiCo-LDH electrodes. Additionally, the Cu 2+1 O@NiCoAl-LDH nanorod arrays, as a positive electrode material, can also be utilized to assemble a hybrid supercapacitor (HSC) device with an activated carbon (AC) electrode (negative electrode). The energy density of the assembled HSC device can up to 61.83 Wh kg−1 with a working voltage of 1.5 V, meanwhile the power density is 749.93 W kg−1. Furthermore, a few Light Emitting Diode (LED) indicators with different shape combination can be lit up by the assembled HSC devices, demonstrating the practicability of the HSC device. A three-dimensional hierarchical core-shell electrode material composed of Cu 2+1 O nanorod arrays branched with NiCoAl-LDH nanosheets exhibits superb capacitance, fast rates, remarkable cycling stability and potential applications. Image 1 • Hierarchical Cu 2+1 O@NiCoAl-LDH nanorod arrays are in situ generated on 3D Cu foams. • Cu 2+1 O@NiCoAl-LDH electrode exhibits superb supercapacitive performance. • The fabricated HSC device demonstrates promising practical applicability. [ABSTRACT FROM AUTHOR]

A hierarchical core-shell heterostructure comprised of vertical and intercrossing ultrathin NiMn-LDHs nanosheets shell and slightly curly and tops tangled CuO nanowires core shows promising electrochemical storage properties. • A hierarchical NiMn-LDH@CuO/CF core-shell heterostructure was successfully prepared. • The hybrid comprises of vertical NiMn-LDHs shell and tops tangled CuO nanowires core. • The NiMn-LDH@CuO/CF electrode exhibits high capacitance of 6077 mF cm−2 at 2 mA cm−2. • The blue LED indicator can be lit up eight minutes by three ASCs connected in series. Supercapacitors are attracting tremendous research interest because they are expected to achieve battery-level energy density while having long calendar life and short charging time. Ultrathin layered double hydroxide nanosheets (LDHs) are promising candidates as electrode materials for energy storage. Herein, we have successfully designed and synthesized a hierarchical NiMn-LDH@CuO/CF core-shell heterostructure which comprises a vertical and intercrossing ultrathin NiMn-LDHs nanosheets shell and a slightly curly and tops tangled CuO nanowires core. The synthesized NiMn-LDH@CuO/CF electrode exhibits a high areal capacitance of 6077 mF cm−2 (2430.8 F g−1) at a current density of 2 mA cm−2 (0.8 A g−1), which is significant higher than those of CF, Cu(OH) 2 /CF, CuO/CF, NiMn-LDH/CF and NiMn-LDH electrodes. Moreover, a superior cycling stability of 89.22% retention after 8000 cycles at a high current density of 50 mA cm−2 is observed and a low internal resistance R s (0.584 Ω) can be achieved. Furthermore, an all solid-state asymmetric supercapacitor (ASC) device based on the as-synthesized hierarchical NiMn-LDH@CuO/CF core-shell heterostructure hybrid material as positive electrode and activated carbon as negative electrode is successfully fabricated and exhibits an energy density of 10.8 W h kg−1 at a power density of 100 W kg−1. Additionally, a LED indicator can be lit up for eight minutes when three ASCs are connected in series. The excellent electrochemical performances can be credited to the significant enhancement of the specific surface area, charge transport and mechanical stability resulted from the ultrathin LDH shell, the highly conductive CuO nanowires core-shell nanostructure. This strategy for the fabrication of hierarchical core-shell heterostructure could have enormous potential for applications in high performance energy storage devices. [ABSTRACT FROM AUTHOR]

The hierarchical nanostructure hybrids of porous Co 3 O 4 nanowires coated NiMn layered double hydroxide nanosheets array on Ni foams (Co 3 O 4 @NiMn-LDH/Ni) are designed and prepared via the two-step hydrothermal reactions with a combination of annealing process. The Co 3 O 4 nanowires can be utilized as backbone to grow the NiMn-layered double hydroxide (NiMn-LDH) nanosheets, which provide a large surface area and leading to the enhanced capacitive performance owing to the effective ion/electron diffusion rates. The areal capacitance of the as-prepared Co 3 O 4 @NiMn-LDH/Ni electrode reaches 19.7 F cm−2 (5419.7 F g−1) at 2 mA cm−2 (0.56 A g−1). Moreover, a high capacitance retention (93.25% of capacitance maintained after 6000 cycles) and a low internal resistance R s (0.62 Ω) can be acquired. Additionally, an all-solid-state asymmetric supercapacitor (Co 3 O 4 @NiMn-LDH/Ni//AC ASC) based on the Co 3 O 4 @NiMn-LDH/Ni as positive electrode and activated carbon (AC) as negative electrode is successfully obtained. The Co 3 O 4 @NiMn-LDH/Ni//AC ASC shows a high energy density of 47.15 Wh kg−1 at 376 W kg−1. Additionally, a LED can be lit up for 12 min when three ASCs are connected in series. Therefore, this novel Co 3 O 4 @NiMn-LDH/Ni with outstanding electrochemical performance should envision potential practical applications in high energy storage appliances. Image 1 • The porous Co 3 O 4 nanowires provide more paths for ions diffusion. • NiMn layered double hydroxide nanosheets provide large surface areas. • Co 3 O 4 @NiMn-LDH/Ni electrode exhibits excellent supercapacitive properties. [ABSTRACT FROM AUTHOR]

Here we report the development of a high-performance electrode material composed of Zn and Ni co-substituted Co carbonate hydroxide (ZnNi-Co 2 (CO 3)(OH) 2) nanothorns branched on Cu(OH) 2 nanorods array (Cu(OH) 2 @ZnNi-Co 2 (CO 3)(OH) 2), which are grown directly on copper foam current collector. The electrode materials are obtained by a simple in situ oxidation reaction and a hydrothermal strategy. The as-obtained Cu(OH) 2 @ZnNi-Co 2 (CO 3)(OH) 2 electrode exhibits significantly enhanced electrochemical performance with a high specific capacitance (2746 F g−1 at 1 A g−1), and extraordinary cycling stability (maintained 95.61% of the initial capacitance after 6000 cycles at 20 A g−1), which are much superior to those of Cu(OH) 2 , Cu(OH) 2 @ Co 2 (CO 3)(OH) 2 , Cu(OH) 2 @Ni-Co 2 (CO 3)(OH) 2 , and bare ZnNi-Co 2 (CO 3)(OH) 2 nanospheres electrodes. Additionally, the Cu(OH) 2 @ZnNi-Co 2 (CO 3)(OH) 2 nanorods array can also be utilized as the positive electrode to fabricate an asymmetric supercapacitor device with an active carbon negative electrode, realizing a high cell voltage of 1.5 V and the energy density of up to 34.75Wh kg−1 at a power density of 375 W kg−1. The excellent electrochemical properties can be credited to the three-dimensional hierarchical core-shell architecture. Image 1 • Hierarchical Cu(OH) 2 @ZnNi-CoCH nanorods array is fabricated on 3D Cu foams. • The materials are obtained by an oxidation reaction and a hydrothermal strategy. • Cu(OH) 2 @ZnNi-CoCH electrode exhibits superb supercapacitive performance. [ABSTRACT FROM AUTHOR]