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Nano core–shell structured materials have different or better properties than single components, which can realize the design and optimization of nanoscale particle structure and properties. Additionally, hollow core–shell materials have the advantages of large specific surface area, abundant active sites, low density, short mass transfer path, and wide cavity structure, which are widely used in the fields of electrochemistry, biomedicine, and environmental protection. Herein, hollow core–shell FeOOH@MnO2 nanorod composites were prepared by easiest hydrothermal method. Due to the synergy and versatility between the hollow FeOOH nanorods core and the MnO2 nanosheets shell, the FeOOH@MnO2 composite exhibits outstanding electrochemical characteristic as an electrode material with specific capacitance of 924 F g−1 at 1 A g−1, admirable rate capability (capacitance retention of 75.9% from 1 to 10 A g−1), and remarkable cycling stability (91.2% of initial capacity retained after 5000 charge/discharge cycles). Notably, the assembled FeOOH@MnO2//activated carbon (AC) asymmetric supercapacitor facility possessed an energy density of 53.4 Wh kg−1 and a power density of 722 W kg−1, indicating that the hollow core–shell FeOOH@MnO2 nanorod nanocomposite is a viable electrode material that can be used in supercapacitors. [ABSTRACT FROM AUTHOR]

In this reported study, novel multiple dimensional ZIF-67/rGO/NiPc composite materials were prepared for supercapacitors. The electrochemical test showed that the ZIF-67/rGO/NiPc electrode achieved a remarkable specific capacitance of 860 F g−1 at a current density of 1 A g−1, which was superior to that of the rGO/NiPc and ZIF-67/rGO electrodes. An asymmetric supercapacitor based on ZIF-67/rGO/NiPc//activated carbon exhibited a high specific capacitance of 200.67 F g−1 and an extraordinary energy density of 62.7 Wh kg−1 at a corresponding power density of 750 W kg−1. In addition, the device demonstrated 94.6% capacitance retention after 5000 cycles. The assembled asymmetric supercapacitors could easily powered a green light-emitting diode. This work revealed a promising research route for the rational construction of multiple dimensioned high-performance electrodes materials for use in new energy storage devices. [ABSTRACT FROM AUTHOR]

The rapid development of wearable and portable smart equipment has led to a research boom in flexible energy storage devices. Herein, NiCo2O4 nanosheet arrays have been successfully grown on carbon fibers (CFs), which was firstly modified by the three-dimensional Ni (3D-Ni) to repair the cracks and grooves in the surface of CF. The obtained CFs@3D-Ni/NiCo2O4 electrode possesses a high specific capacity of 736 F/g at 1 A/g current density in the three-electrode system. More importantly, the composite showed excellent electrochemistry stability after temperature plummets. The all-solid-state asymmetric supercapacitor device (ASC) assembled by CFs@3D-Ni/NiCo2O4 delivers a wonderful specific capacity of 176 F/g, a high energy density 55 W h/Kg at 750 W/Kg, excellent cycling stability (about 97.84% after 2000 cycles), and high flexibility (almost no influence in electrical performance at various bending angles). This work has provided a promising method to prepare high performance of the flexible and lightweight energy storage equipment. [ABSTRACT FROM AUTHOR]

Fe-based oxide electrodes for practical applications in supercapacitors (SCs) suffer from low conductivity and poor structural stability. To settle these issues, we report on the design and synthesis of Fe 3 O 4 /carbon nanocomposites via firmly anchoring mesoporous Fe 3 O 4 nanospheres onto N-doped carbon nanotubes (N-CNTs) via C–O–Fe bonds. Mesoporous Fe 3 O 4 nanospheres are featured by rich electroactive sites and short ion diffusion pathways. The N-CNTs, on the other hand, serve as the scaffolds, which not only provide conductive networks but also suppress the accumulation between mesoporous Fe 3 O 4 nanospheres as well as alleviate volume changes during charge/discharge cycles. Accordingly, the constructed Fe 3 O 4 /N-CNTs nanocomposite electrode demonstrates improved specific capacity values of up to 314 C g−1 at 1 A g−1, with 92% retention of the initial capacity after 5000 cycles at 10 A g−1. In addition, the assembled Fe 3 O 4 /N-CNTs//active carbon (AC) asymmetric supercapacitor (ASC) device possesses an energy density of 25.3 Wh kg−1, suggesting that the prepared Fe 3 O 4 /N-CNTs nanocomposites are promising electrode materials for use in SCs. [ABSTRACT FROM AUTHOR]

Herein, we report on layer‐by‐layer MnCo2O4/NiMn double hydroxide (LDH) nanosheet arrays (NAs) that are designed and synthesized by in‐situ growing the NiMn LDH NAs onto the surface of the MnCo2O4 NAs. The layer‐by‐layer architecture together with the synergistic effects between the NiMn LDH and MnCo2O4 components, substantially improves the energy storage performance of the composite NAs electrodes. The optimized composite NAs electrode exhibits a high specific capacitance of 3063 F g−1 at 3 A g−1 (four times with respect to the individual MnCo2O4 electrode), a capacitance retention of 2315 F g−1 at 30 A g−1, and a cycle stability with 94.7 % capacitance retention at 20 A g−1 over 5000 cycles. Moreover, an assembled MnCo2O4/NiMn LDH//active carbon (AC) asymmetric solid‐state supercapacitor (ASSC) is found to achieve a high energy density of 51.9 W h kg−1 at 806 W kg−1. These findings might offer a feasible strategy to synthesize the high‐performance MnCo2O4‐based composite electrodes for supercapacitors (SCs). Layer‐by‐layer: hierarchical MnCo2O4/NiMn layered double hydroxide nanosheet arrays are designed and synthesized as supercapacitor electrode with significantly enhanced electrochemical performance. A solid‐state asymmetric supercapacitor is assembled, using activated carbon as counter electrode. The device exhibits a high energy density, showing the promising potential of the presented strategy for the synthesis of high‐performance materials. [ABSTRACT FROM AUTHOR]

The original version of this article was inadvertently misplaced Fig. 1a and Fig. 1c with each other. The correct results are showed as follows. [ABSTRACT FROM AUTHOR]

The practical applications of transition-metal oxides as electrode materials for supercapacitors are still impeded by their intrinsically poor electrical conductivity and limited number of electroactive sites. Herein, a defect engineering strategy combined with interface engineering is adopted to create nitrogen-doped bismuth molybdate (N-BMO) hollow nanostructures decorated with graphene quantum dots (GQDs). Theoretical calculation and experimental results indicate that the N doping in BMO can enhance electrical conductivity of N-BMO by reducing its electronic band gap. Moreover, the surface decoration of GQDs on N-BMO enables higher electrical conductivity and more electroactive sites. More importantly, a built-in electric field is formed at the N-BMO/GQD interface due to their Fermi-level difference, which favors fast interfacial charge transfer and accelerate electrode reaction kinetics. Accordingly, the optimized N-BMO@GQD electrodes yield higher specific capacities (572 and 435 C g−1 at 1 and 10 A g−1, respectively) and better cycling stability (91 % capacity retention after 10000 cycles at 5 A g−1) compared to pristine BMO electrode. Moreover, an assembled asymmetric supercapacitor device with N-BMO@GQD as positive electrode can deliver an energy density of 45.2 Wh kg−1 at 801 W kg−1. This study showcases an efficient strategy to design and develop promising BMO-based electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

To fulfill the promise of high-performance supercapacitors (SCs) with a high specific capacitance, superior rate capability, long cycling life, and high energy density, it is desirable to rationally construct core-shell composite electrode materials with tailored architectures and components. In this reported study, hierarchical Zn 0.76 Co 0.24 S@Ni 3 S 2 core-shell nanosheet arrays (CSNAs) on Ni foam are designed and synthesized, in which interconnected Zn 0.76 Co 0.24 S nanosheet cores are initially constructed through a hydrothermal reaction combined with a sulfurization process. These nanosheet cores are then uniformly wrapped by a Ni 3 S 2 nanosheet shell using an electrochemical deposition reaction. The hierarchical structure of nanosheets@nanosheets together with the synergistic effect between the Zn 0.76 Co 0.24 S and Ni 3 S 2 components, enables the composite electrode to exhibit a large specific capacity (1209 C g −1 at 2 A g −1 ), good rate capability (78.6% capacity retention at 20 A g −1 ), and remarkable cycle stability (94.9 capacity retention after 5000 cycles at 20 A g −1 ). Furthermore, the fabricated Zn 0.76 Co 0.24 S@Ni 3 S 2 //active carbon (AC) asymmetric solid-state supercapacitor cell (ASSC) can deliver a high energy density of 53.8 W h kg −1 at a power density of 853 W kg −1 . These results showcase the great application potential of the novel core-shell composite electrode in high-performance SCs, and they also provide an alternative method for constructing metal sulfide-based composite electrodes with optimum electrochemical performance. [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDHs) as electrode materials for supercapacitors still suffer from limited actual specific capacities and unsatisfactory cycling performance owing to their poor intrinsic electrical conductivity and insufficient electroactive sites. Herein, oxygen vacancy (Ov)-rich CoAl-LDH nanosheets are attached onto reduced graphene oxide (rGO) nanosheets to form 2D/2D Ov-CoAl-LDH/rGO sheet-on-sheet heterostructures via a facile precipitation-reduction reaction followed by hydrothermal treatment. The introduction of rich Ov defects in CoAl-LDHs enhances the electrical conductivity, while the attachment of Ov-CoAl-LDH nanosheets on the surface of rGO nanosheets not only reduces the aggregation of Ov-CoAl-LDH nanosheets and thus exposes abundant electroactive sites, but also maintains good structural stability. Theory calculations indicate that the Fermi-level difference of two components triggers interfacial charge separation while creating a built-in electric field at the Ov-CoAl-LDH/rGO interface, which favors rapid electron/ion migration and accelerates charge storage kinetics. The optimized Ov-CoAl-LDH/rGO nanocomposites deliver specific capacities of 984 C g−1 at 3 A g−1 and 708 C g−1 at 20 A g−1 and retain an initial capacity of 90 % after 10,000 cycles at 10 A g−1. These findings showcase a feasible strategy to endow 2D/2D LDHs/graphene heterostructures with enhanced charge storage performance. [Display omitted] • 2D/2D Ov-CoAl-LDH/rGO sheet-on-sheet heterostructures are constructed. • rGO serves as supports to reduce the aggregation and size of Ov-CoAl-LDH nanosheets. • The W F difference induces charge density distribution at Ov-CoAl-LDH/rGO interface. • Ov-CoAl-LDH/rGO electrodes exhibit enhanced charge storage performance. [ABSTRACT FROM AUTHOR]

Layered double hydoxides (LDHs) as electrode materials for supercapacitors still suffer from unsatisfactory rate capability owing to their limited electrical conductivity and sluggish ion diffusion kinetics. In this work, a vacancy engineering strategy coupled with a nanocomposite method is proposed to construct oxygen vacancy (Ov)-rich CoAl-LDH nanosheets coupled with N-doped carbon nanotubes (N-CNTs) using a one-step precipitation-reduction reaction. Experimental analyses and theoretical calculation results indicate that the rich Ov defects in CoAl-LDHs not only effectively enhance the electrical conductivity but also reduce the surface adsorption barrier of electrolyte ions, thereby triggering fast charge storage kinetics. In addition, Ov-rich CoAl-LDH nanosheets coupled with N-CNTs are well dispersed, which not only enrich electroactive sites but also further increase the charge transport. Consequently, the obtained N-CNT@Ov-CoAl-LDH nanocomposites demonstrate a specific capacity of 1068 C g−1 at 3 A g−1 and maintain a capacity retention of 78% even at 20 A g−1, together with a capacity retention of 91% after 10,000 cycles at 10 A g−1. This work provides insights for designing and engineering LDHs-based electrodes with improved charge storage performance through coupling the vacancy engineering with the nanocomposite method. [Display omitted] [ABSTRACT FROM AUTHOR]

Rational design and fabrication of core-shell nanoarrays (CSNs) with distinctive architectures and desirable capacitive performances are believed to be a promising and challenging strategy toward advanced electrode materials for supercapacitors (SCs). In this work, we report a two-step synthesis of three-dimensional (3D) MnCo 2 O 4 nanosheets@MnMoO 4 nanosheets CSNs on Ni foam (NF), which are constructed by vertically growing MnMoO 4 nanosheets onto interconnected MnCo 2 O 4 nanosheets arrays (NAs). Such MnCo 2 O 4 @MnMoO 4 CSNs can make full use of its unique 3D architecture and the synergistic effect between MnCo 2 O 4 and MnMoO 4 . Therefore, the prepared MnCo 2 O 4 @MnMoO 4 CSNs, as a binder-free electrode for SCs, demonstrate a significantly enhanced specific capacity (885 C g −1 at 3 A g −1 ), higher rate capability (629 C g −1 at 30 A g −1 ), and better cycling stability (95% capacitance retention after 5000 cycles at 10 A g −1 ) compared with the single MnCo 2 O 4 or MnMoO 4 NAs electrode. Moreover, the assembled asymmetric SC cell (ASC) based on MnCo 2 O 4 @MnMoO 4 //activated carbon (AC) also exhibits a specific capacity (222 C g −1 at 1 A g −1 ) and an energy density (49.4 W h kg −1 at 815 W kg −1 ), indicating a promising practical application for the prepared MnCo 2 O 4 @MnMoO 4 CSNs in high-performance SCs. [ABSTRACT FROM AUTHOR]

Core/shell nanorods of MnO 2 /carbon embedded with Ag nanoparticles (MCA) were successfully fabricated via a facile and effective hydrothermal and reduction method in situ. Typically, a MCA-1.5 sample (1.5 g·L −1 glucose reactant) exhibited the highest specific capacitance of 628 F·g −1 at the current density of 1 A·g −1 in three-electrode systems. Particularly, a fabricated asymmetric supercapacitor, using MCA-1.5 and active carbon as the positive and negative electrodes, respectively, delivered a maximum energy density of 48.3 W·h·kg −1 at power density of 851.7 W·kg −1 and exhibited a superior, long cycle life, showing ∼98.5% specific capacitance retention after 2000 cycles. The practical energy-storage applicability of this device was demonstrated by the operation of an LED bulb when a duo of two such devices was charged. These results indicated that synthesized ternary nanocomposites have potential applications as supercapacitor electrodes in energy storage systems. [ABSTRACT FROM AUTHOR]

Despite considerable efforts have been devoted to the design and synthesis of advanced electrode materials for supercapacitors (SCs), it is still a huge challenge to achieve high-performance electrode materials with the large practical capacity and high rate capability. Herein, novel self-supported MnCo 2 O 4 @Ni 3 S 2 core–shell heterostructures (CSHs) as a binder-free electrode are rationally designed and constructed by homogeneously growing Ni 3 S 2 nanosheets onto the hexagonal prism-like MnCo 2 O 4 microstructures on Ni foam (NF). Impressively, compared with the pristine MnCo 2 O 4 and Ni 3 S 2 electrodes, the prepared MnCo 2 O 4 @Ni 3 S 2 CSHs electrode demonstrates a remarkably enhanced specific capacitance (2807 F g −1 at 3 A g −1 ) along with a significantly improved rate capability (69% capacitance retention at 30 A g −1 ). These findings not only suggest the promising application of self-supported MnCo 2 O 4 @Ni 3 S 2 CSHs as advanced SCs electrode materials but also provide an alternative way for constructing next-generation high-performance SCs with remarkably improved electrochemical performance. [ABSTRACT FROM AUTHOR]

In this work, we reported the synthesis of three dimensional flower-like Co 3 O 4 @MnO 2 core-shell microspheres by a controllable two-step reaction. Flower-like Co 3 O 4 microspheres cores were firstly built from the self-assembly of Co 3 O 4 nanosheets, on which MnO 2 nanosheets shells were subsequently grown through the hydrothermal decomposition of KMnO 4 . The MnO 2 nanosheets shells were found to increase the electrochemical active sites and allow faster redox reaction kinetics. Based on these advantages, when used as an electrode for supercapacitors, the prepared flower-like Co 3 O 4 @MnO 2 core-shell composite electrode demonstrated a significantly enhanced specific capacitance (671 F g −1 at 1 A g −1 ) as well as improved rate capability (84% retention at 10 A g −1 ) compared with the pristine flower-like Co 3 O 4 electrode. Moreover, the optimized asymmetric supercapacitor device based on the flower-like Co 3 O 4 @MnO 2 //active carbon exhibited a high energy density of 34.1 W h kg −1 at a power density of 750 W kg −1 , meaning its great potential application for energy storage devices. [ABSTRACT FROM AUTHOR]

In this study, reduced graphene oxide (rGO)-wrapped dandelion-like CuO microspheres have been successfully synthesized using a one-step hydrothermal method without calcination. Characterization results demonstrate that dandelion-like CuO microspheres with sizes of 2.0 μm are well wrapped by ultrathin rGO nanosheets. Moreover, the introduced amount of GO dispersion in the reaction system was found to play a key role in tuning the phase compositions and microstructures of the resultant CuO-rGO composites. When used as electrode materials for supercapacitors, dandelion-like CuO wrapped by rGO nanosheets exhibited the best capacitive behavior with a specific capacitance of 296 F g −1 at 1.0 A g −1 and a retention of 96.1% after 2000 cycles at 2.0 A g −1 . Such excellent electrochemical performance might be mainly attributed to the rGO wrapping effect, efficiently providing higher electronic conductivity and buffering the volume changes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ternary NiCo 2 Al 0.02 -LDH/ N - Cc @PANI electrode have been synthesized. • A novel porous hollow capsule structure of nitrogen-doped carbon is designed and used as a conductive matrix material. • NiCo 2 Al 0.02 -LDH/ N - Cc @PANI electrode exhibits a fascinating capacitance of up to 1630F/g. • The assembled device could easily power a LED bulb. This paper designs and produces ternary NiCo 2 Al x -LDH grown directly on a novel porous hollow structure of nitrogen-doped carbon capsule (N - Cc) conducting matrix with a PANI coating layer. The carefully designed NiCo 2 Al x -LDH/ N - Cc @PANI electrodes exhibit electrochemical properties that are highly prized for their energy storage utility: specifically, a gravimetric capacitance of 1630F/g, an energy density of 55.75 Wh kg−1 at the power density of 750 W kg−1, and cyclic stability that achieves capacitance retention of 93.1 % after 5000 uninterrupted charge–discharge cycles. It should be noted that the electrode's excellent storage performance benefitted from the use of Al, which was crucial in stabilizing the LDH structure. It should also be pointed out that the 3D interconnected porous structure composed of N - Cc provides a greater accessible surface area and shortens the ion/electron transport distance, whilst PANI ensuring the LDHs remain firmly in contact with the conductive substrate. [ABSTRACT FROM AUTHOR]

Hollow mesoporous PPy@MnO 2 composites were successfully synthesized by a low-temperature redox reaction. The synthesized hollow mesoporous PPy@MnO 2 electrode has outstanding electrochemical properties with a specific capacitance of 713 F g−1 at 1 A/g and a 92% retention rate after 5000 cycles at 4 A/g. The asymmetric supercapacitor constructed using PPy@MnO 2 as the positive electrode material achieved a high energy density of 40.8 Wh kg−1 at a power density of 720 W kg−1, and the capacitance retention rate can be maintained at 90.5% after 5000 charge/discharge cycles at 5 A/g. [Display omitted] • Hollow mesoporous PPy@MnO 2 composite were successfully synthesized by a low-temperature redox reaction. • PPy@MnO 2 composite with hollow mesoporous core–shell structure had good performance in supercapacitor. • The asymmetric supercapacitor devices assembled with PPy@MnO 2 composite possess remarkable cycling stability (90.5 % after 5000 cycles at 5 A g−1) and high energy density (40.8 Wh kg−1 at the power density of 720 W kg−1). In this work, hollow mesoporous PPy microspheres were prepared by using mesoporous SiO 2 as a hard template, and hollow mesoporous PPy@MnO 2 composites were successfully synthesized by a low-temperature redox reaction. The unique heterogeneous structure can realize the complementary advantages of the two materials. PPy can be used as a template to support the whole structure, and the design of the hollow structure will further buffer the volume change during cycling. In addition, the mesoporous structure will further increase its specific surface area and porosity, thereby enhancing the stability of its overall structure and internal electron transport, and significantly increasing the number of active sites. Thus, the synthesized hollow mesoporous PPy@MnO 2 electrode has outstanding electrochemical properties with a specific capacitance of 713 F g−1 at 1 A g−1 and a 92 % retention rate after 5000 cycles at 4 A g−1. The asymmetric supercapacitor constructed using PPy@MnO 2 as the positive electrode material achieved a high energy density of 40.8 Wh kg−1 at a power density of 720 W kg−1. This work inspires a simple idea for designing hollow mesoporous nanocomposite electrodes with excellent electrochemical performance and provides a high-performance supercapacitor material for its practical applications. [ABSTRACT FROM AUTHOR]

Novel flower-like MnCo 2 O 4 hollow microspheres have been synthesized through a facile template-free solvothermal method combined with calcination. The as-synthesized flower-like MnCo 2 O 4 hollow microspheres have a diameter of 3.0 μm, and constructed by numerous loosely arraying nanoflakes with a thickness of 20 nm. Based on their unique flower-like and hollow structures, these flower-like MnCo 2 O 4 hollow microspheres display a good capacitive behavior with a specific capacitance of 235.7 F g −1 at a current density of 1.0 A g −1 and a good specific capacitance retention of 93.6% after 2000 continuous charge–discharge cycles. The excellent capacitive properties and stability suggest that these flower-like MnCo 2 O 4 hollow microspheres could be promising electroactive materials for supercapacitors. [ABSTRACT FROM AUTHOR]

Fe 3 O 4 @PPy@MnO 2 ternary core-shell nanospheres are synthesized by facile solvothermal, in-situ polymerization, and redox reactions.The nanocomposite exhibits excellent electrochemical performance with specific capacitance of 751F g−1 at 1 A/g and remarkable cycling stability (87.0% capacitance retention after 5000 cycles at 4 A/g). The asymmetric supercapacitor devices assembled with Fe 3 O 4 @PPy@MnO 2 nanocomosite possess remarkable cycling stability (95.2% after 5000 cycles at 5 A/g) and high energy density (71.3 Wh kg−1 at the power density of 750 W kg−1). [Display omitted] • Fe 3 O 4 @PPy@MnO 2 ternary core-shell nanospheres are synthesized. • The electrode exhibits high specific capacitance and good cycling stability. • The asymmetric supercapacitor devices possess high energy density. The rapid development of supercapacitors has led to increasing demand for electrode materials with excellent electrochemical properties. In this study, Fe 3 O 4 @PPy@MnO 2 nanocomposites with porous core and double-shell layers were successfully synthesized and utilized as supercapacitor electrode materials. Specifically, a dense PPy coating is formed on the porous Fe 3 O 4 surface to ensure high structural stability, and a MnO 2 shell layer could be easily introduced on the PPy surface through the redox reaction between PPy and KMnO 4. The prepared composite electrode material has the advantages of high specific surface area, short diffusion distance of electrolyte ions, good electron transfer, and fast and reversible Faraday reaction. The Fe 3 O 4 @PPy@MnO 2 electrode not only exhibits high specific capacitance (751F g−1 at 1 A/g), but also exhibits excellent cycling stability (87.0 % capacitance retention after 5000 cycles at 4 A/g). This is owing to the synergistic effect of the porous Fe 3 O 4 core, the dense PPy coating, and the MnO 2 nanosheet shell. Furthermore, the asymmetric supercapacitor devices assembled with Fe 3 O 4 @PPy@MnO 2 nanocomosite possess remarkable cycling stability (95.2 % after 5000 cycles at 5 A/g) and high energy density (71.3 Wh kg−1 at the power density of 750 W kg−1). These results demonstrate the great potential of Fe 3 O 4 @PPy@MnO 2 nanocomposites with porous cores and double shells as electrode materials for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

• Ag nanoparticles are anchored onto CuS sub-micron flowers to form composites. • The CuS@Ag electrodes exhibit enhanced charge storage property. • The decoration of Ag nanoparticles increases the electrical conductivity. • The generated electric field at the CuS/Ag interface accelerates the charge transfer. [Display omitted] In this reported work, Ag nanoparticles (NPs) decorated CuS sub-micron flowers are synthesized using a facile, solvothermal reaction coupled with a silver mirror reaction. The experimental results and theoretical calculations reveal that decorating the CuS with Ag NPs increases its intrinsic electrical conductivity and generates an electric field at the interface between Ag and CuS. These effects promote the efficient utilization of active materials and accelerate the interface charge transfer and electrochemical reaction kinetics. Consequently, the maximum specific capacity of the prepared CuS@Ag electrodes is found to be as high as 702 C g−1 at 2 A g−1, which is about 5 times greater than the pure CuS electrode. In addition, the capacity value is 400 C g−1 at 20 A g−1 and it exhibits 93% retention of the initial capacity after 5000 cycles at 10 A g−1. Moreover, a hybrid supercapacitor (HSC) device is assembled employing the CuS@Ag electrode as the positive electrode, which delivers an energy density of 51.1 Wh kg−1 at a power density of 798 W kg−1. These results demonstrate the promising potential of the fabricated CuS@Ag composites for further application in HSCs. [ABSTRACT FROM AUTHOR]

• Amorphous CoS x nanoparticles are anchored onto N-CNTs to form nanocomposites. • A diffusion-controlled charge storage behavior prevails in CoS x /N-CNTs electrodes. • CoS x /N-CNTs nanocomposites exhibit enhanced rate capabilities and cyclic stability. • Amorphous CoS x and N-CNTs work together to improve the energy storage property. ga1 Cobalt sulfide has been considered as one kind of promising battery-type electrode material (BTEM) for hybrid supercapacitors (HSCs). However, unsatisfactory rate capability and cyclic stability still hinder its further practical application in high-performance HSCs. Here, amorphous CoS x nanoparticles are anchored onto N-doped carbon nanotubes (N-CNTs) to form CoS x /N-CNTs nanocomposites by a chemical bath deposition (CBD) and subsequent sulfurization reaction. Originating from the synergistic effect of amorphous CoS x nanoparticles and flexible N-CNTs conductive backbones in the nanocomposites, the prepared CoS x /N-CNTs nanocomposites exhibit enhanced specific capacities (899 C g−1 at 3 A g−1 and 611 C g−1 at 20 A g−1) and long-term cyclic stability (initial capacity retention of 94% after 5000 cycles at 10 A g−1) compared with CoS x and N-CNTs electrodes. In addition, a HSC device is fabricated using CoS x /N-CNTs and N-CNTs as the positive and negative electrodes, respectively, which can deliver an energy density of 51.9 Wh kg−1 at a power density of 800 W kg−1. Therefore, the constructed CoS x /N-CNTs nanocomposites hold promise for designing high-performance cobalt sulfide-based electrode materials for further practical application in HSCs. [ABSTRACT FROM AUTHOR]

Carbon based supercapacitor suffers from low energy density due to inefficient electrical double-layer storage mechanism. Herein, sp3-defect engineered sp2 carbon framework with hierarchical porous architecture (HCF) is developed via a one-step chemical vapor deposition (CVD) method for high energy density supercapacitor. Theoretical calculations are performed firstly and results reveal that the sp3-defects in host sp2 carbon sheets promote the sodium-ion storage performance attributed to the reduced energy barrier of sodium-ion adsorption and increased density of states around Fermi level. The HCF is extensively characterized and the results show that the density of sp3-defects and hierarchical micro-meso-macropore size of HCF can be well tuned by regulating the CVD temperature. Owing to reasonably engineered sp3-defects (~32.8 at%), well-defined multiscale pore architectures and wide interlayer in HCF, extra pseudocapacitive sodium-ion storage sites are obtained and therefore a capacitance up to 558.8 F/g is achieved. The resultant HCF based symmetric supercapacitor device gives a high energy density of 38.76 Wh/kg at a power density of 375.04 W/kg and still retains 30.00 Wh/kg at a high power density of 5970.15 W/kg. This work provides a facile strategy to explore the intrinsic defect in carbon electrode materials for high performance energy storage systems. Image 1 • DFT calculation demonstrates that sp3-defects contribute to improved Na+ storage. • sp3-Defect rich porous carbon framework (HCF) is developed for supercapacitors. • The sp3-defect density and hierarchical pore-size of HCF can be easily tunable. • HCF employed as supercapacitor electrode show a high capacitance of 558.8 F g-1. • HCF based symmetric supercapacitor delivers a high energy density of 38.76 Wh kg−1. [ABSTRACT FROM AUTHOR]