Biomass-Derived Nitrogen and Sulfur Co-Doped 3D Carbon Networks with Interconnected Meso-Microporous Structure for High-Performance Supercapacitors

Three-dimensional (3D) carbon networks have been explored as promising capacitive materials thanks to their unique structural features such as large ion-accessible surface area and interconnected porous networks, thus enhancing both ions and electrons transport. Here, sustainable bacterial cellulose (BC) is used both precursor and template for facile synthesis of free-standing N, S-codoped 3D carbon networks (a-NSC) by the pyrolysis and activation of polyrhodanine coated BC. The synthesized a-NSC shows highly conductive interconnected porous networks (24 S•cm^-1), large surface area (1 420 m²•g^-1) with hierarchical meso-microporosity, and high-level heteroatoms codoping (N: 3.1 % in atom, S: 3.2 % in atom). Benefitting from these, a-NSC as binder-free electrode exhibits an ultrahigh specific capacitance of 340 F•g^-1 (24 μF•cm^-2) at the current density of 0.5 A•g^-1 in 6 M KOH electrolyte, high-rate capability (71% at 20 A•g^-1) and excellent cycle stability. Furthermore, the assembled symmetrical supercapacitor displays a much short time constant of 0.35 s in 1 M TEABF₄/AN electrolyte, obtaining a maximum energy density of 32.1 W•h•kg^-1 at power density of 637 W•kg^-1. The in situ multi-heteroatoms doping enables biocellulose-derived carbon networks to exploit its full potentials in energy storage applications, which can be extended to other dimensional carbon nanostructures.