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Designing high-performance electrodes and elucidating their energy storage mechanisms are crucial for supercapacitors. In this study, an in situ conversion method is firstly employed to transform CoCH (Co(CO 3) 0.5 (OH)·0.11 H 2 O) into Co-MOF-74 nanorods, which serves as a self-sacrificial template. Subsequently, the amorphous CoMoS 4 hollow tube arrays with self-assembled nanosheet surfaces are obtained through MoO 4 2- etching and S2- exchange. Benefiting from the nanosheets-coated hollow tubular structure and amorphous characteristics, CoMoS 4 exhibits a high areal capacitance of 7.01 F·cm−2 at 2 mA·cm−2 and 91.81 % retention after 5000 cycles. When further assembled into a hybrid supercapacitor, the CoMoS 4 //AC device exhibits excellent performance with the energy density of 0.684 mWh·cm−2 at 1.876 mW·cm−2 and 91.39 % retention after 10000 cycles. Furthermore, the mechanism study reveals that Mo- and S-doped amorphous CoOOH is a genuine energy storage material. This work provides valuable insights into the preparation of amorphous materials using the self-sacrificial template transformation method and the understand of their energy storage mechanisms. [Display omitted] • Amorphous CoMoS 4 hollow tube array exhibits excellent specific capacitance and cycling stability. • CoMoS 4 exhibits a high areal capacitance of 7.01 F·cm−2 at a current density of 2 mA·cm−2. • CoMoS 4 exhibits high cycling stability with 91.81 % capacity retention after 5000 cycles. • CoMoS 4 //AC device demonstrates remarkable cycling stability with capacitance retentions of 91.39 % after 10000 cycles. [ABSTRACT FROM AUTHOR]

Abstract Four morphology-dependent ZnCo 2 O 4 nanoarchitectures on Ni-foam with the aid of auxiliary reagent ammonium fluoride (NH 4 F) were facilely synthesized via a simple hydrothermal method and a consequent annealing process. With the gradual increase of NH 4 F, there was a morphological transformation from nanoflake, through nanowire@nanoflake and hetero-nanowire, to hierarchical leaf-like. The BET surface area and the specific capacitance at 1 A g−1 were both gradually improved, from 63.9 to 89.3 m2 g−1 and from 600 to 1700 F g−1, respectively, during the process of morphological change. The hierarchical leaf-like ZnCo 2 O 4 had the lowest charge transfer resistance and the highest capacitive behavior, as well as considerable cycling performance (110% after 8000 cycles at 2 A g−1). A full button cell combining both anode material (AC) and cathode material (leaf-like ZnCo 2 O 4) displayed satisfying energy density (63 Wh kg−1) and power density (795.5 W kg−1) as well as firm cycling performance (98% retention after 4000 cycles). The successful illumination of LEDs by the constructed full cell implied the promising practicability for future industrial green energy-storage devices usage of the ZnCo 2 O 4 nanomaterials. Graphical abstract Image 1 Highlights • Four ZnCo 2 O 4 nanostructures on Ni foam with disparate morphologies are fabricated. • Among the four electrodes, the leaf-like ZnCo 2 O 4 exerts the highest specific capacitance, excellent cycling ability. • A full cell device based on AC anode and the leaf-like ZnCo 2 O 4 cathode has been successfully fabricated. • The full cell device delivers a high energy density of 63 Wh kg−1 at the power density of 795.5 W kg−1 [ABSTRACT FROM AUTHOR]

Transition metal sulfides are gaining attention as a new highly capacitive active material for high-performance supercapacitors, however, it is still a challenge that synthesizes a distinctive structure to enhance the electrochemical characteristics and practical applications. In this work, hierarchical structural hybrid metal sulfides (NiCo 2 S 4 /Co 4 S 3) based on nanosheets and nanocages are synthesized by sulfurating the NiCo-LDH/ZIF-67 precursors. The NiCo 2 S 4 /Co 4 S 3 electrode with remarkable layered and porous structure effectively increase the electrochemical active surface area and accelerate the charge transfer, achieving a high specific capacitance of 8.43 F cm−2 at a current density of 2 mA cm−2 and good cyclic stability. An assembled asymmetric supercapacitor with activated carbon delivers a high energy density of 0.50 mWh cm−2 at a power density of 1.69 mW cm−2. These results demonstrate that NiCo 2 S 4 /Co 4 S 3 is an ideal electrode material for high-performance electrochemical energy storage devices. [Display omitted] • NiCo 2 S 4 /Co 4 S 3 displays a hierarchical structure based on nanosheet and nanocage. • NiCo 2 S 4 /Co 4 S 3 achieves a high specific capacitance and good cyclic stability. • An assembled asymmetric supercapacitor delivers a high energy density. • NiCo 2 S 4 /Co 4 S 3 is an ideal electrode material for high-performance supercapacitor. [ABSTRACT FROM AUTHOR]

Bimetal oxides have superior supercapacitive properties because of synergistic effect, but their applications are usually limited because of low conductivity. Metal cations doping has been a promising method to break the restriction. Here, we first selected CuCo 2 O 4 nanowire arrays with high electrochemical activity as mother bimetal oxides and Al3+ with high electric conductivity as the dopant to investigate the influence of doped amounts on the electrochemical behaviors. With the increase of doped Al3+, the specific capacitance increased at first and then decreased, in accord with the analysis results of the conductivity, capacitive and diffusion-controlled contribution. The sample with the optimal doping amount had the highest capacitive behavior (1871 F g−1 at 1 A g−1) and considerable cycling performance (93% after 8000 cycles at 2 A g−1). A full button cell consisting of anode material (AC) and cathode material (the optimal Al-doping CuCo 2 O 4) exhibited satisfied energy density (65 Wh kg−1) and power density (735 W kg−1) as well as favorable cycling performance (95% retention after 4000 cycles). A LED was successfully powered by the constructed full cell suggested the promising application in future industrial green energy-storage devices of the Al-doping CuCo 2 O 4 nanomaterials. Image 1 • Al3+ was doped into CuCo 2 O 4 nanowires to investigate the influence of doped amounts on the electrochemical behaviors. • With the increase of doped Al3+, the specific capacitance increased at first and then decreased. • A full cell device based on AC anode and the optimal Al-doping CuCo 2 O 4 cathode has been constructed. • The full cell device exhibited a high energy density of 65 Wh kg-1 at the power density of 735 W kg-1. [ABSTRACT FROM AUTHOR]