Polypyrrole Nanotube-Interconnected NiCo-LDH Nanocages Derived by ZIF-67 for Supercapacitors

Layered double hydroxides (LDHs), composed of typical lamellar architectures, have become splendid electroactive materials for supercapacitors by means of large specific surface area and high theoretical capacitance. However, severe agglomerations and poor conductivities of single LDHs are disadvantageous to obtain the excellent electrochemical performance. Herein, polypyrrole nanotubes (PNTs) with good conductivity and mechanical capacity were prepared for in situ growth of ZIF-67, and the obtained PNT@ZIF-67 nanocomposites could serve as effective sacrificial templates and Co2+ sources. After a facile solvothermal reaction and acid etching, three-dimension hierarchical PNT-interconnected nickel cobalt-layered double hydroxide (PNT@NiCo-LDH) nanocages were successfully synthesized to construct the supercapacitors, in which the formed networking hierarchical structure could facilitate the uniform distribution of ZIF-67-derived NiCo-LDH nanocages, not only providing an enhanced conductivity and cycling stability but also achieving outstanding specific capacitance (1448.2 F g–1 at 1 A g–1). Additionally, the asymmetric supercapacitor, assembled by positive PNT@NiCo-LDH and negative activated carbon, could achieve an excellent energy density of 64.4 Wh kg–1 at 800 W kg–1 and endure a satisfactory cycling stability with 84.3% capacitance retention over 5000 cycles, which was superior to the electrochemical properties of the NiCo-LDH-dependent asymmetric supercapacitor, showing a promising prospect in high-performance supercapacitors.