Flexible and high energy density asymmetrical supercapacitors based on core/shell conducting polymer nanowires/manganese dioxide nanoflakes

Abstract Hierarchically porous polypyrrole nanowires/manganese oxides nanoflakes (MnO 2 NFs@PPy NWs) core/shell nanostructures were successfully constructed through a simple, convenient and environmentally friendly method by using PPy nanowires as the core buffer and K-Birnessite type MnO 2 as the shell. The core/shell nanostructures effectively increase active surface areas and decrease the ion transmission distance, which is conducive to the efficient transfer of ions. The MnO 2 NFs@PPy NWs core/shell nanostructures exhibited not only high specific capacitance (276 F g −1 at 2 A g −1 ) but also excellent capacitance retained ratio of 72.5% under extreme charge/discharge conditions (200 F g −1 at 20 A g −1 ) due to the synergistic effect by combining the merits of MnO 2 and PPy. Using such hierarchical nanostructure as the positive electrode, we further demonstrate that ultra-flexible asymmetrical supercapacitors (AFSCs) (MnO 2 @PPy//AC) possess excellent cycling stability (90.3% after 6000 cycles at 3 A g −1 ), mechanical flexibility, large voltage operation window (1.8–2.0 V vs. SCE) and high energy densities at all charge/discharge conditions (25.8 W h kg −1 at the power density of 901.7 W kg −1 , and 17.1 W h kg −1 at the power density of 9000 W kg −1 , respectively).