Paper-Derived Flexible 3D Interconnected Carbon Microfiber Networks with Controllable Pore Sizes for Supercapacitors

Heteroatom-doped three-dimensional (3D) carbon fiber networks have attracted immense interest because of their extensive applications in energy-storage devices. However, their practical production and usage remain a great challenge because of the costly and complex synthetic procedures. In this work, flexible B, N, and O heteroatom-doped 3D interconnected carbon microfiber networks (BNOCs) with controllable pore sizes and elemental contents were successfully synthesized via a facile one-step "chemical vapor etching and doping" method using cellulose-made paper, the most abundant and cost-effective biomass, as an original network-frame precursor. Under a rational design, the BNOCs exhibited interconnected microfiber-network structure as expressways for electron transport, spacious accessible surface area for charge accumulation, abundant mesopores and macropores for rapid inner-pore ion diffusion, and lots of functional groups for additional pseudocapacitance. Being applied as binder-free electrodes for supercapacitors, BNOC-based supercapacitors not only revealed a high specific capacitance of 357 F g^-1, a high capacitance retention of 150 F g^-1 at 200 A g^-1, a high energy density of 12.4 W h kg^-1, and a maximum power density of 300.6 kW kg^-1 with an aqueous electrolyte in two-electrode configuration but also exhibited a high specific capacitance of up to 242.4 F g^-1 in an all-solid-state supercapacitor.