Free-Standing and Heteroatoms-Doped Carbon Nanofiber Networks as a Binder-Free Flexible Electrode for High-Performance Supercapacitors

Flexible and heteroatoms-doped (N, O and P) activated carbon nanofiber networks (ACFNs) have been successfully prepared with a mixture of polyamic acid (PAA) and poly(diaryloxyphosphazene) (PDPP) as a solution through electrospinning, followed by a heat post-treatment. The resultant heteroatoms-doped ACFNs can be used as binder-free electrodes for high-performance flexible supercapacitors (SCs) due to lightweight, three-dimensional open-pore structure and good mechanical strength. Despite its surface area being lower than 130.6 m2·g−1, the heteroatoms-doped ACFNs exhibited a high heteroatoms (N, O and P) content of 17.9%, resulting in a highly specific capacitance of 182 F·g−1 at a current density of 1 A·g−1 in 6 M KOH electrolyte in a two-electrode cell and an excellent rate capability of 74.7% of its initial capacitance from 1 A·g−1 to 10 A·g−1 under the mass loading of 1.5 mg·cm−2. The electrical double-layer (EDL) capacitance and pseudocapacitance can be easily decoupled in the heteroatoms-doped mesoporous ACFNs. SCs device based on heteroatoms-doped ACFNs exhibited a high energy density of 6.3 W·h·kg−1 with a power density of 250 W·kg−1, as well as excellent cycling stability with 88% capacitance retention after 10,000 charge−discharge cycles. The excellent electrochemical performance was attributed to the mesoporous structure of ACFNs and pseudocapacitive heteroatoms.