Decoration NiCo2S4 nanoflakes onto Ppy nanotubes as core-shell heterostructure material for high-performance asymmetric supercapacitor

In this work, a unique Ppy@NiCo2S4 core-shell heterostructure material is prepared taking polypyrrole (Ppy) nanotubes as skeleton through a simple and environmentally friendly hydrothermal method. The heterostructured structure with Ppy nanotubes (NTs) as the core and intertwined flake-like NiCo2S4 as the outer shell, holds a large specific surface area (217 m(2) g(-1)), convenient charge transport channel, high specific capacitance (908.1 F g(-1) at a current density of 1 A g(-1)), and excellent cycling performance (87.7% of initial value is retained after 2000 cycles). What's more, an asymmetric supercapacitor is fabricated by employing Ppy@NiCo2S4 core-shell heterostructured material as positive and nitrogen-doped carbon nanotubes (N-C NTs) as negative electrode. This Ppy@NiCo2S4//N-C asymmetric supercapacitor effectively provides a high energy density over 50.82 Wh kg(-1) with a high power density of 160 W kg(-1) and preeminent cyclic stability of 126.6% after 2000 cycles. Due to the introduction of one-dimensional flexible Ppy inner core, as-designed the core-shell heterostructure composite may be promising in the flexible energy storage devices.