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Reasonable construction of electrodes materials with heterostructures is a very effective way to enhance the electrochemical performance. Herein, a series of hybrid electrodes materials (PPy/Ni–Co LDH) based on nickel-cobalt layered double hydroxide (Ni–Co LDH) with zeolitic imidazolate framework-67 (ZIF-67) as the template and polypyrrole (PPy) nanotubes have been synthesized. Various precursors PPy/ZIF-67 based on polypyrrole nanotubes with the same amount have been prepared, where the mass ratio of polypyrrole nanotubes to ZIF-67 are varied in the process of crystallization. As-synthesized precursors PPy/ZIF-67 serve as sacrificial templates and give birth to various hybrid electrodes materials PPy/Ni–Co LDH with the core-shell structure, where Ni–Co LDH is closely coated on the external surface of polypyrrole nanotubes. The experimental findings reveal the electrochemical performance of PPy/Ni–Co LDH becomes better and better with increasing masses of Ni–Co LDH. Benefiting from their core-shell structure and the synergy effect between polypyrrole nanotubes and Ni–Co LDH, the optimized sample displays a specific capacitance of 13.0 F cm−2 (1858.3 F g−1) at 1 mA cm−2 and a favorable rate capability. Furthermore, a symmetric coin-type hybrid supercapacitor based on the optimized sample has also been fabricated, and exhibits an energy density of 10.425 mWh·cm−2 at the power density of 0.25 mW cm−2. Hybrids PPy/Ni-Co LDH are used for supercapacitors and show high specific capacitances via synergistic effect between Ni-Co LDH and PPy. Image 1 • Polypyrrole inter-connected hollow Ni/Co LDH hybrids are prepared. • Their performance are better and better with increasing Ni–Co LDH masses. • The optimum sample displays a capacity of 13 F/cm2 and a favorable rate capability. • Their performance can attribute to the synergy effect between PPy and Ni–Co LDH. [ABSTRACT FROM AUTHOR]

With the increasing demand for preparing energy storage devices, composites containing metal oxides, have been widely developed and used as supercapacitors. However, the electrochemical performances of such materials are unable to be satisfied owing to the inherent poor conductivity. Herein, we employ "in-situ pyrolysis" approach to fabricate composite electrode materials without binding agents, which are obtained by the direct calcination of the mixture MnO 2 and poly (vinylidene difluoride) coated on carbon cloths, generating a family of binder-free electrode materials BE-X. For comparison, another family of electrode materials CE-X have been obtained through the conventional method. Naturally, two different families of electrode materials are prepared and exhibit different electrochemical performances. In general, the performances of electrode materials prepared by an "in-situ pyrolysis" approach are better than those of electrode materials via the conventional method, indicating the enhanced adhesion between electrode materials and current collectors could be benefit for the electrochemical process. Among all prepared electrode materials, BE-7 exhibits the best performance (5.44 F cm−2 at 5 mV s−1) as well as a good rate stability. Furthermore, a flexible symmetric supercapacitor device based on BE-7 is also prepared, and exhibits an areal capacitance of 100.50 mF cm−2. Two family of electrodes prepared by different methods exhibit varied performances, where the performances of binder-free electrodes prepared by the in-situ pyrolysis approach are better than those of electrodes by the conventional methods. Image 1 • An efficient binder-free electrode has been prepared simply through "in-situ pyrolysis" approach. • The electrodes prepared by different methods result in different performances. • The performance of binder-free electrodes are better than those of electrodes prepared by conventional electrodes. • A flexible symmetric supercapacitor device exhibits an areal capacitance of 100.5 mF cm−2. [ABSTRACT FROM AUTHOR]