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Scalable assembly of two dimensional (2D) lamellar nanomaterials for deformable films has potential in wearable energy storage devices, but overcoming the trade‐off in mechanical and energy storage properties is a challenge. Here, a blade‐coating strategy is reported to develop highly stretchable and bendable metal‐organic frameworks/large‐sized Ti3C2Tx MXene (MOF/LMX) composite films on the pre‐stretched elastomer substrates. The LMX sheets serve as conductive scaffolds for loading the small‐sized ultrathin MOF sheets (SUMOFs), resulting in an improved tensile strength (≈97 MPa) of the films, which guarantees their structural integrity when forming a wavy structure on a relaxed substrate. In addition, SUMOFs incorporated in‐between LMX layers not only expose active redox sites by mitigating the intrinsic self‐restacking of MOF but also accelerate the electron transfer in the redox reaction process revealed through the density functional theory calculations. As a result, the composite films deliver high electrical conductivity (3244 S cm−1) and energy storage capability (1238 F g−1). When assembled into an asymmetric supercapacitor device, it also exhibits stable performances under different bending and stretching states. Thus, the development of conducting and deformable MOF‐based films with high mechanical, electrical, and energy storage properties enables their potential commercial applications for wearable electronics. [ABSTRACT FROM AUTHOR]

Zn‐ion hybrid capacitors (ZHCs), combined with features of rechargeable batteries and double‐layer supercapacitors, are considered as one of the most promising energy storage devices due to their high energy and power density. However, there are still many challenges in developing ideal carbon cathode to match the high capacity of Zn anode. In this work, an activated carbon aerogel (ACA) with hierarchical porous structure is successfully prepared via freeze‐drying, carbonization and KOH activation process. Thanks to the high accessible specific surface area, rational pore size distribution and N, O co‐doping, the as‐assembled ZHC based on the optimal sample exhibits high capacity of 299.5 F g−1 (133.1 mAh g−1) at 0.1 A g−1, excellent rate capability of 57.6 % capacity retention even at 20‐fold higher current, together with good cycling stability (86.3 % capacity retention after 10000 cycles at 2 A g−1). More gratifyingly, it also displays impressive energy density of 106.5 Wh kg−1, satisfactory power density of 3108 W kg−1, and promising potential for practical applications. Based on our results, the ACA could be one of the promising candidates for carbon cathodes for ZHCs. [ABSTRACT FROM AUTHOR]

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]

Recently, three‐dimensional‐structure materials have attracted enormous attention in energy‐storage fields on account of their excellent electrochemical performance. In this study, hierarchical nanospheres consisting of mesoporous CoO@CuO nanowires on a three‐dimensional conductive Ni foam are prepared by a one‐step hydrothermal method combined with a subsequent annealing process. Compared to CoO or CuO alone, the as‐obtained CoO@CuO/Ni hybrid nanowires show good electronic conductivity owning to the abundant existence of O vacancies in them. In a three‐electrode system, the area capacitance of the prepared CoO@CuO/Ni electrode reaches 2.94 F cm−2 (1.32 C cm−2) at 1 mA cm−2, and the CoO@CuO/Ni electrode presents an outstanding cycle performance. Moreover, a CoO@CuO/Ni//AC ASC asymmetric supercapacitor is fabricated and found to display a high energy density of 20.22 Wh kg−1 at 800 W kg−1. Hence, this novel CoO@CuO/Ni hybrid nanowires with excellent electrochemical properties shows outstanding potential in the practical application of high‐energy storage devices. [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]

Novel nanomaterials and advanced nanotechnology continuously push forward the rapid development of sustainable energy conversion and storage equipment. An emerging family of two‐dimensional transition‐metal carbides, nitrides and carbonitrides, also known as MXenes, have attracted increasing attention and in depth investigation. Benefitting from their unique intrinsic properties, MXenes have attracted significant attention and they have been considered as promising candidate materials for the development of environmentally friendly energy resources. A large number of studies show that MXenes have great potential in energy conversion and storage fields. Despite of their exceptional properties, MXenes also have some inherent characteristics, such as low capacities and unstable retention performances, which severely hinder their prospect applications in energy conversion and storage fields. In this Minireview, the latest progress on MXenes and their hybrid composites with small molecules, polymers, carbon or metal ions, and their applications in energy conversion and storage fields is highlighted, including their use in different types of batteries, supercapacitors, hydrogen/oxygen evolution reactions, electromagnetic interference absorption/shielding and solar steam generation. In addition, the critical challenges and further development prospects of MXene‐based materials are also introduced. [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]

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]

Laminated and scale-like Ni/Zn-MOF/ZnO@CC hybrid materials with high orientation are synthesized and exhibit promising electrochemical properties. [Display omitted] Metal-organic frameworks (MOFs) are attracting tremendous research interest because of their rich redox sites and high specific area which are beneficial for the energy storage applications. Nevertheless, the poor conductivity, low mechanical strength and unsatisfactory capacity severely hinder their wide application. Hence, it is of practical significance to design highly efficient and facile strategy to solve these issues. Herein, vertically oriented ZnO nanorod arrays are applied as precursor to synthesize laminated scale-like and highly-oriented Ni/Zn-MOF/ZnO nanocomposite. Owing to the desirable conductivity resulting from the doping nickel ions and the interaction between ZnO and its relative MOF, the fabricated 0.3Ni/Zn-MOF/ZnO@CC electrode exhibits an electrochemical capacitance of 1693 mF cm−2 at 1 mA cm−2. Moreover, the electrochemical capacitance retention of 80.7 % after 2500 cycling numbers is obtained under the constant current density of 10 mA cm−2 and the low internal resistance R s of 0.89 Ω is observed. For practical application, the as-synthesized laminated scale-like Ni/Zn-MOF/ZnO@CC nanocomposite is served as positive electrode to fabricate solid-state asymmetric supercapacitor device. Moreover, a 2.5 V indicator could be powered for 8 min when the prepared supercapacitor units are connected. This work demonstrates the promising potential of the synthesized scale-like Ni/Zn-MOF composites for electrochemical energy storage applications. [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]

• 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]

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]

• 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]

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]

[Display omitted] • Porous NCS nanosheets are prepared by a one-step method. • CS@NCS/CC core–shell hetero-nanostructure with abundant mesopores is constructed. • Flexible CS@NCS/CC electrode can be bent and twisted at multiple angles. • CS@NCS/CC electrode exhibits excellent electrochemical performance. • CS@NCS/CC//AC/CC device continuously lights up a small bulb for 12 min. Flexible portable supercapacitor devices have gained increasing attention in the field of energy storage in recent years. However, challenges remain in the selection of applicable flexible materials and/or the preparation of materials. Through our research, we have effectively constructed a flexible CS@NCS/CC core–shell hetero-nanostructured cathode material by anchoring Co 9 S 8 (CS) nanopins on a flexible carbon cloth (CC) substrate firstly, and then wrapping NiCo 2 S 4 (NCS) nanosheets on the outer surface of CS nanopins. In this process, we have improved the traditional two-step method of preparing NCS nanosheets into a one-step method, which has greatly improved the efficiency of the material preparation. The prepared CS@NCS/CC material has abundant mesopores, stable core–shell heterostructures and multiple valence states of metal ions, which enable the CS@NCS/CC electrode material to have strong electrochemical reaction kinetics and excellent cycling stability. Additionally, the CC as the flexible substrate improves the charge transfer capability of the transition metal composite. Benefiting from the synergistic effect of these favorable factors, the electrode material exhibits a high C s value of 2020.6F g−1, which maintains 89.8% after 10,000 constant current charges and discharges. It is worth noting that the CS@NCS/CC can be folded and twisted at multiple angles, which proves that it can be used in wearable applications. The flexible hybrid supercapacitor CS@NCS/CC//AC/CC displays terrific energy density (58 Wh kg−1, at 800 W kg−1) with the synergistic effect of pseudocapacitance and electrical double-layer capacitance, and a capacitance retention rate of 92.9% after 10,000 cycles of constant current charging and discharging. Therefore, using CC as the flexible substrate and transition metal sulphides as the active material is an effective strategy for constructing high-performance flexible supercapacitors. [ABSTRACT FROM AUTHOR]

• Stretchable film assembled by large sized MXene shows excellent structural integrity. • Wave-like patterns of the films can be controlled through the pre-stretched elastic substrates. • The stretchable MXene film electrode achieves balanced electrical, mechanical and energy storage properties. • The stretchable supercapacitor device exhibits stable energy storage performances after 1000 tensile-release cycles. Ti 3 C 2 T x MXene with superior electrical, mechanical and electrochemical properties has attracted tremendous interest in flexible electronics. However, it remains challenging to transfer these prominent properties to stretchable MXene films with uncompromising properties due to the small flake size and weak interlayer interactions of MXene. Here, by using large sized MXene (LMX, ∼10 μm) with continuous overlap rate, and the synergistic effects of covalent and hydrogen bonds between PVA and LMX, we achieve stretchable polyvinyl alcohol (PVA)/LMX films that can simultaneously possess high mechanical strength (∼280 MPa), electrical conductivity (∼6240 S cm−1) and energy storage capability (∼364F g−1) under different tensile strains ranging from 0 to 150 %. The as-assembled stretchable supercapacitor device demonstrates high capacitance retention of nearly 100 % under stretching rates at 50 %, 100 % and 150 %, or bending rates at 90° and 180°. Impressively, the device also displays good reliability and safety that can maintain its performances under repeated stretching (at 100 % strain) or bending (180°) after 1000 cycles. Thus, the development of stretchable MXene based films with uncompromised properties is expected to broaden their applications for wearable electronics in future commercialization. [ABSTRACT FROM AUTHOR]

Transition metal quantum dots (QDs) have attracted enormous attention in the field of energy storage in recent years due to their unique nano-size effect and flexible surface functionalities. It is worth noting that the aggregation of QDs will lead to the decline of electrochemical performance, so it is necessary to maintain its good dispersion stability. Bi-pyrene-terminated molecular wires (BPMW) can reduce the stacking of graphene, which is considered to be a good material for modifying graphene with desired porous structure, higher specific surface area, and more attachment sites for the loading of QDs. Here, rGO@BPMW@CoCeS x -QDs were successfully designed and constructed. In detail, CoCe bimetallic organic framework (CoCe-MOF) was grown in situ on BPMW modified graphene by two-step solvothermal method to afford porous composites of rGO@BPMW@CoCeS x -QDs (pore size range is 40–230 nm). The fabricated electrode based on rGO@BPMW@CoCeS x -QDs shows an excellent electrochemical capacitance of 1047 F g−1 at the current density of 1 A g−1 in a three-electrode system. Moreover, a solid-state asymmetric supercapacitor (ASC) device can be fabricated based on the synthesized rGO@BPMW@CoCeS x -QDs, and exhibits a high energy density of 32.3 Wh kg−1 at a power density of 750 W kg−1. [Display omitted] • CoCeS x -QDs were prepared from CoCe-MOF by solvothermal method. • BPMW-modified graphene has a pore size range of 40–230 nm. • The rGO@BPMW@CoCeS x -QDs electrode has excellent electrochemical performance. • The assembled ASC device has practical application prospects. [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]

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]

Nanostructured carbon materials have shown promising applications for energy storage because of their high capacitive characteristic. However, developing three-dimensional (3D) hierarchical carbon materials with both high compressibility and capacitance is still challenging. Herein, we report the fabrication of hierarchical polypyrrole (PPy)/graphene (reduced graphene oxide (G) and holey reduced graphene oxide (h-G))/melamine composite foam through a simple template method. By systematically optimizing the mass ratios of the G/h-G and the sizes of the PPy nanoparticles (PPy NPs), the as-prepared composite electrode displays a gravimetric capacitance of 422.6 F g−1 at a current density of 0.5 A g−1. Due to the interconnected h-G/G network and elastic melamine foam (MF) skeleton, the as-prepared composite electrode also shows compressible performance, which can be compressed to a strain of 60% and completely recover to its original shape when released. When the composite electrodes are assembled to a compressible supercapacitor which shows a stable capacitance under different compressive strains (0%, 25%, 50% and 75%) and a long-term compression test at 50% strain for 100 cycles. Therefore, the successful preparation of compressible composite electrode should open many opportunities in compressible and durable energy storage devices. Three dimension (3D) hierarchical PPy/graphene/melamine foam composite electrodes are fabricated for the assembly of highly compressible supercapacitor which exhibits stable electrochemical performance under different compressive strains (0%, 25%, 50% and 75%) or after 100 compression/release cycles under a compressive strain of 50%. Image 1 • 3D hierarchical composite electrode was obtained through a template method. • Connected rGO network renders the electrode with high compressibility. • PPy and the hierarchical structure makes the electrode with high capacitance. • The compressible SCs show good reliability under different compressive states. [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]