Flexible heteroatom‐doped porous carbon nanofiber cages for electrode scaffolds

Abstract Porous carbon nanofibers (PCNFs) with rich functionalities and high surface areas are important electrode scaffolds to load active materials, but increasing their pore volumes and strength simultaneously is a challenge. Here, we report a scalable method to fabricate B‐F‐N triply doped PCNF cages with high porosity of greater than 92.8% and small bending stiffness of 10 mN by electrospinning the mixed sol of poly(tetrafluoroethylene), poly(vinyl alcohol), boric acid, and carbon nanotubes (CNTs) followed by pyrolysis. The macro‐micro dual‐phase separation creates well‐controlled macropores (>60 nm) and meso‐micropores with large pore volumes (0.55 cm³/g) on carbon nanofibers, while the interior CNTs can cushion the applied stress and render the PCNF films with superior flexibility. Fabricated symmetrical supercapacitors with the PCNF cages exhibit high gravimetric capacitance of 164 F/g at 20 mV/s and 92.5% capacity retention after 20 000 cycles at 2 A/g. The reported approach allows the green synthesis of a new PCNF scaffold material with properties appealing for applications.