The application of nanocellulose/N, S co-doped graphene composite and novel PVA-based electrolyte in high-performance supercapacitors

Heteroatom doping and good porous structure play a decisive role in the energy storage characteristic of graphene-based supercapacitors. In this study, nanocellulose/N, S co-doped graphene composite hydrogel (NC-NSGHs) electrode materials were successfully prepared by a one-step hydrothermal method. During the reaction, ammonium sulfate was used as heteroatom source and reducing agent, nanocellulose (NC) was used as spacer and electrolyte storage container, and high a concentration of graphene oxide (GO, 4 mg mL⁻¹) was used to increase the bulk density of the material. The target product NC-NSGHs have ideal pore structure, good hydrophilicity, and rich heteroatom functional groups. The aqueous symmetrical supercapacitors (SCs) assembled by NC-NSGH-50 exhibits high gravimetric specific capacitance (0.3 A g⁻¹, 280.6 F g⁻¹), volumetric specific capacitance (0.3 A g⁻¹, 406.9 F cm⁻³), excellent rate performance (20 A g⁻¹, 81.06%) and superior cyclic performance. In addition, we added GO and NC into the PVA-KOH electrolyte system and developed a new gel electrolyte PVA-GN-KOH (PGNK). The flexible solid-state supercapacitors (FSSCs) fabricated by PGNK and NC-NSGHs display a high specific capacitance of 189.9 F g⁻¹ (0.5 A g⁻¹). Even at 20 A g⁻¹, the rate performance of the device can reach 60.24%. The emergence of NC-NSGHs and PGNK provides new ideas for high-performance portable supercapacitors.