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Cobalt iron phosphide (Co–Fe–P), a metalloid-like material with zero band gap and high specific capacity, has received much attention in the field of supercapacitors, but the poor rate performance and cycling stability limit its commercial applications. Herein, we used cobalt-iron metal organic framework as the precursor (under the modulation of the polyvinylpyrrolidone (PVP), the morphology changes from three-dimensions to one-dimension), to synthesize the Co–Fe–P@NiCo-layered double hydroxide (LDH) core–shell nanostructure on conductive nickel foam (NF). Profiting of high conductivity of Co–Fe–P nanowires as the core and large surface area of NiCoLDH nanosheets as the shell, the fabricated Co–Fe–P@NiCoLDH/NF electrode exhibits outstanding electrochemical properties, such as high special capacity of 5.67 C cm−2 at a current density of 1 mA cm−2, remarkable rate capability (78.59% from 1 to 20 mA cm−2). Moreover, the asymmetric supercapacitor assembled by Co–Fe–P@NiCoLDH/NF and activated carbon/NF, also delivers excellent electrochemical performance with high energy density of 0.164 mW h cm−2 (30.4 mW h cm−3) and a superior cyclic life span of 91.67% over 5000 cyclic tests under 20 mA cm−2. This work proposes a unique route for the application of Co–Fe–P with elaborate structures, which may excite new significant findings in the energy storage field. [ABSTRACT FROM AUTHOR]

Cobalt‐based sulfide is an excellent electrode material applied to supercapacitors (SCs) because of its good reversibility and abundant nanoforms. However, the feasibility of its practical application is reduced due to lack of stability and some difference with theoretical capacity. Herein, the hierarchical structures of Co3S4 hollow nanotube arrays wrapped with NiCo‐layered double hydroxide nanosheets (Co3S4@NiCo‐LDHs) are successfully fabricated on the nickel foam (NF) as the nonbinder electrode of SCs. Profiting from the synthetic effect of Co3S4 hollow nanotube arrays with effective diffusion channels, and NiCo‐LDH nanosheets with a stable interconnected network, the prepared Co3S4@NiCo‐LDH/NF composite electrode with a unique hierarchical structure attains an amazing areal capacity (7.45 C cm−2 at 2 mA cm−2) and impressive cycle stability (87.7% through 5000 charge and discharge cycles). In addition, the assembled asymmetric supercapacitor (Co3S4@NiCo‐LDH/NF//AC) shows pleasant energy density (0.661 mWh cm−2 under 1.359 mW cm−2). The capacity of the assembled device can still be retained at 92% after 5000 cycles, which verifies the feasibility of the device in practical application. [ABSTRACT FROM AUTHOR]

Although many researches have been made in the construction and fabrication of electrode materials for supercapacitors, it remains a difficult task to realize the application of the supercapacitor with high energy density. The binary MnCo2O4@NiO hierarchical electrode has been successfully fabricated on nickel foam (NF) without any binder or additives by simple hydrothermal methods and corresponding annealing processes. By virtue of constructing hierarchical core–shell structure with different morphologies and forming additive-free electrode, the composite electrode not only possesses abundant surface active sites for electrochemical reaction as well as large buffering space for volume deformation in the charging-discharging processes, but also shows the improved contacting area and electric conductivity between active substance and metal collector. The synthetic MnCo2O4@NiO/NF electrode presented higher specific capacitance (1186 F g−1 under 1 A g−1) and long cycle lifespan (maintain 91% of the original capacitance over 5000 cycles) under a high current density of 10 A g−1. Further, the asymmetric supercapacitor with MnCo2O4@NiO/NF electrode shows higher energy density of 42.2 Wh kg−1 under a power density of 748.2 W kg−1. These results demonstrate that the binary MnCo2O4@NiO hierarchical structure is the hopeful candidate material for high performance supercapacitor electrode. [ABSTRACT FROM AUTHOR]

• We successfully fabricate GF@MNT@MNF as lightweight and free-standing supercapacitor electrode. • MnO 2 mass percentage affects significantly on the electrochemical properties of the composite electrode. • GF@MnO 2 -60% electrode presents higher specific capacitance and excellent cycling stability. Three-dimensional graphene foam (3D GF) is one of the promising candidates due to its fascinating characteristics. In the paper, we reported a simple hydrothermal method to fabricate hierarchical α-MnO 2 nanotube@δ-MnO 2 nanoflake on GF (GF@MNT@MNF) as a lightweight and free-standing electrode of supercapacitor. The 3D GF could serve as an ideal supporter to grow MnO 2 active material, and MnO 2 mass percentage affects significantly on the electrochemical properties of the composite electrode. When the mass percentage of MnO 2 is 60%, a maximum specific capacitance of 202 F·g−1 with respect to the entire electrode and 336 F·g−1 relative to active material is achieved. The GF@MNT@MNF electrode presents a remarkable cyclic stability (maintaining about 97% of original capacitance over 5000 cycles). The excellent electrochemical performance of the GF@MNT@MNF electrode is resulted from the combination of the lightweight, flexible, conductive GFs and MnO 2 hierarchical structure with large contacting interface and proper space distribution. Furthermore, an asymmetric supercapacitor based on GF@MNT@MNF composites was assembled, which showed a great energy density of 23.2 Wh·kg−1 under a power density of 119.9 W·kg −1 in wide potential range of 0–1.8 V. The research may provide a method for lightweight, free-standing and high-performance electrode material for efficient and convenient energy storage device. [ABSTRACT FROM AUTHOR]

With a facile spraying chemical vapor deposition technique and a subsequent hydrothermal method, well dispersed Co 0.85 Se nanoparticles supported on a stable frame of vertically oriented carbon nanotube (VOCNT) were synthesized and pressed directly on nickel foam (NF) for additive-free supercapacitor electrode. The fabricated electrode (VOCNT@Co 0.85 Se/NF) displayed a high specific capacity of 638 F g−1 under 1 A g−1, a good rate performance (87.8% capacity maintaining when the current density increased from 1 to 30 A g−1), and a remarkable cyclic stability (about 97.3% of the capacity retention over 5000 charging-discharging cycles). The excellent properties of VOCNT@Co 0.85 Se/NF electrode could be ascribed to the involvement of the VOCNT with uniquely aligned structure and proper intertube distance, which is helpful to the quick transport of electron/ions and reduces the volume deformation during various charging-discharging tests to effectively prevent the internal structure collapsing. Furthermore, the assembled asymmetric device based on the VOCNT@Co 0.85 Se/NF electrode possesses a energy density of 21.47 Wh·kg−1 at 325 W kg−1. This research reveals that unique VOCNT@Co 0.85 Se/NF could be regarded as potential candidate electrode with super cycle stability and rate performance for supercapacitors. • We fabricate successfully VOCNT@Co 0.85 Se/NF as an additive-free supercapacitor electrode. • The VOCNT@Co 0.85 Se/NF electrode presents remarkable rate capability and cycling stability at higher specific capacitance. • The VOCNT with unique and stable structure is responsible for superior electrochemical properties. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract A novel hierarchical core-shell nanocolumn array, with NiCo 2 S 4 hollow nanowire (NiCo 2 S 4 H-NW) as the core and NiCoP nanosheet (NiCoP NS) as the shell, has been directly synthesized on nickel foam (NF) as self-supported, binder-free electrode for high-performance supercapacitors. The morphological characterizations reveal that the diameter of NiCo 2 S 4 H-NW core is ∼100 nm and the diameter of single NiCo 2 S 4 @NiCoP core-shell nanocolumn is ∼250 nm. Through a series of electrochemical tests and the analysis of charge storage kinetics, hierarchical NiCo 2 S 4 @NiCoP/NF electrode presents high areal specific capacitance of 5.98 F/cm2 at 1 mA/cm2, outstanding rate capability (70.29% capacitance retention with the current density increased from 1 to 50 mA/cm2) and superior cycling stability (92.94% of original capacity is retained after 5000 cycles at 10 mA/cm2). The prominent performance of NiCo 2 S 4 @NiCoP/NF electrode could be resulted from their unique hierarchical core-shell nanocolumn structure, which could offer abundant active sites near the interface for fast electrochemical reaction, and validly avoid the collapse of internal structure for the stability of whole structure in the repeated electrochemical measurement. The novel NiCo 2 S 4 @NiCoP/NF electrode offers a new method for future electrochemical energy storage devices with high-stability. [ABSTRACT FROM AUTHOR]

• We successfully fabricate bimetallic perovskite fluorides/rGO composite materials for the supercapacitor electrode. • The dual effects of B-site regulation and the addition of rGO on the electrochemical properties have been explored. • NaCo 0.2 Ni 0.8 F 3 /rGO composite electrode exhibits higher specific capacitance and excellent structure stability. Perovskite fluoride is a potential electrode material for supercapacitors because its high theoretical specific capacitance. However, the relatively poor cyclic stability and rate performance limit its practical application. In this paper, we successfully synthesized the bimetallic perovskite fluorides/reduced graphene oxide (NaCo 0.2 Ni 0.8 F 3 /rGO) composite materials through a simple solvothermal method. The effects of the Co/Ni ratio regulation and the addition of rGO on the electrochemical properties of the perovskite composite materials have been investigated in detail. The variable valence metal ions by Co/Ni ratio regulation can lead to multiple redox reactions, which are helpful to improve the specific capacity of the materials. Meanwhile, the addition of rGO could improve the cycle stability and rate performance by virtue of the great conductivity of the rGO and the uniform dispersion of perovskite nanoparticles on it. The NaCo 0.2 Ni 0.8 F 3 /rGO composite electrode displays the high specific capacity of 805.7 C g−1, excellent rate performance (82% capacity retention from 0.5 to 16 A g−1) and superior cycle stability (92% retention over 5000 cycles). Furthermore, the active carbon//NaCo 0.2 Ni 0.8 F 3 /rGO asymmetric supercapacitor exhibits a high energy density of 52.19 Wh kg−1 under a power density of 750 W kg−1. It is believed that the above findings supply an efficient electrode design for the future practical application of perovskite fluorides in high-performance supercapacitor. [ABSTRACT FROM AUTHOR]