Hierarchical BiO nanosheets and ZIF-8 derived porous nitrogen-doped carbon fibers as novel assembled nanocomposites for high-performance flexible supercapacitors.

The unique design of the core-shell heterostructure is significant for obtaining electrode materials with excellent electrochemical properties. In this paper, porous carbon nanofibers (NPC@PPZ) embedded with N-doped porous carbon nanoparticles are used to construct flexible electrodes (NPC@PPZ@BiO). Zeolite imidazole skeleton (ZIF)-8 and poly(methyl methacrylate) (PMMA) derived porous carbon fibers and BiO nanosheets, were utilized as the porous core and multilayer shell, respectively. The unique core and shell result in abundant pores and channels for fast ion transport and storage, high specific surface area, and additional electroactive sites. This perfect structural design enables the NPC@PPZ@BiO composite electrode to have excellent electrochemical performance. The results show that this electrode can obtain a high specific capacitance of 697 F g at a current density of 1 A g and a stable cycling performance at a high current density of 5 A g. The strategy developed in this study provides a new approach for the design and fabrication of flexible supercapacitors by electrostatic spinning combined with hierarchical porous structures.