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• 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]

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]

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]

Compressible and flexible supercapacitors have aroused enormous interest of many scientific researchers for potential applications in wearable electronic products. However, the design and construction of the electrode with superior mechanical as well as electrical properties still face a lot of challenges. In present work, melamine foam/polypyrrole (MF/PPy) electrode with high deformation-tolerance and excellent electrochemical performance is prepared by in-situ interfacial polymerization of polypyrrole on commercial melamine foam, where PPy nanoparticles with size of 700 nm are uniformly anchored on the MF skeletons. The electrochemical characterizations show that the electrode exhibits excellent specific area capacitance of 2.685 F cm−2 at 2 mA cm−2 and good cyclic stability with more than 80% of capacitance remained after 3000 cycles. Furthermore, a symmetrical aqueous supercapacitor is assembled and exhibits an excellent energy density up to 75.95 μWh cm−2 at the power density of 5.82 mW cm−2 and excellent cycling stability as the current density increases by 10 times. Even under a high strain of 70%, about 95.76% of the initial capacitance is retained after 500 consecutive compressions. These outstanding performances enable the MF/PPy composite a promising candidate for potential applications in compressible and flexible electrochemical energy storage devices. [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]

• 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]

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]

Recently, elemental doping has proven to be an efficient method to improve the electrochemical performance of nanomaterials. In this work, we successfully synthesized Ni 1-x Co x MoO 4 with tunable morphologies through Co-doping by a facile chemical co-precipitation method, among which Ni 0.85 Co 0.15 MoO 4 displays an excellent specific capacitance (1301 F g−1 at 1 A g−1), which is higher than NiMoO 4 electrode (1050.4 F g−1 at 1 A g−1) and Ni 0.7 Co 0.3 MoO 4 electrode (755.2 F g−1 at 1 A g−1). In addition, Ni 0.85 Co 0.15 MoO 4 electrode shows excellent cycling stability with 86% retention of its original capacitance after 3000 cycles. Additionally, an asymmetric supercapacitor (ASC) device can be fabricated using Ni 0.85 Co 0.15 MoO 4 /nickel foam (Ni 0.85 Co 0.15 MoO 4 /NF) as positive electrode and active carbon/nickel foam (AC/NF) as negative electrode. The as-fabricated ASC achieves a high energy density of 37.26 Wh kg−1 at the power density of 400 W kg−1, highlighting its potential application for the efficient energy storage devices. Image 1 • This work proposed a facile chemical co-precipitation method for the synthesis of Ni 1-x CoxMoO 4 with tunable morphologies. • Different morphologies of Ni 1-x Co x MoO 4 were obtained by adjusting the Co doping ratio. • The Ni 0.85 Co 0.15 MoO 4 electrode exhibits excellent specific capacitance of 1301 F g−1 at 1 A g−1. [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]