Porous NiCo2O4@Ppy core-shell nanowire arrays covered on carbon cloth for flexible all-solid-state hybrid supercapacitors

Nanoarray structure materials have drawn much attention because they facilitate the transmission of electrons and shorten ion diffusion path for application in energy storage. In this paper, the porous core-shell NiCo2O4@Ppy nanowire arrays were designed and successfully prepared through hydrothermal treatment assisted with sodium dodecyl sulfate as a template and sequent by electrochemical deposition of polypyrrole. The structural characterization results show that the 8–40 nm thickness of polypyrrole layer is covered on crystalline NiCo2O4 nanowires. The electrochemical tests verified that the unique NiCo2O4@Ppy composite exhibits fast charge transfer kinetics during long charge/discharge process. The specific capacity of the NiCo2O4@Ppy/CC electrode reaches 155.4 mAh g−1 at the density of 1 mA cm−2 and 138 mAh g−1 at 10 mA cm−2. Also, it exhibits the 71% capacity retention ratio after 8000 cycles at 10 mA cm−2. Furthermore, an all-solid-state hybrid supercapacitor, assembled by the NiCo2O4@Ppy/CC as positive electrode, active carbon as negative electrode and PVA/KOH gels as electrolyte, delivers high energy and power density. The excellent electrochemical performance of the core-shell structure NiCo2O4@Ppy reveals the great possibility for the application in high-performance supercapacitors.