NiCoO₂ and polypyrrole decorated three-dimensional carbon nanofiber network with coaxial cable-like structure for...

Designing optimized nano-sized architecture is a promising approach to prepare high-performance electrode materials for supercapacitors. In this work, a hierarchical multi-shelled structure has been successfully synthesized, which consists of a 3D carbon nanofiber network as a supporting scaffold prepared by carbonization of aramid nanofiber aerogel, an intermediate polypyrrole (PPy) bonding layer and a NiCoO₂ outer shell, just like a coaxial cable in the structure. The intermediate PPy layer facilitates the uniform deposition of NiCoO₂ by providing more anchor sites, and enhances the electrical contact between carbon nanofiber network and NiCoO₂ shell due to its high conductivity and good compatibility with two different substances. The synergistic effect of the hierarchical configuration endows the electrode material with a high specific capacitance of 1037 F g^-1at 1 A g^-1and excellent cycling stability (∼89% of initial capacitance after 7000 cycles). Moreover, an asymmetric supercapacitor based on the composite and activated carbon achieves a high energy density of 37.7 Wh kg^-1 at a power density of 465 W kg^-1 in 1.65 V. This work may provide a feasible strategy to design high-performance hybrid electrodes for energy storage devices.