Scalable fabrication of hierarchically porous graphene fibers via hydrothermal self-assembly and GO-assisted wet-spinning for high-performance flexible supercapacitors

The scalable fabrication of porous graphene fibers remains a critical challenge in developing flexible supercapacitors, particularly in maintaining structural homogeneity and consistent electrochemical performance during scale-up processes. Here, we demonstrate a scalable synthesis strategy that combines hydrothermal self-assembly pretreatment with a graphene oxide (GO)-assisted wet-spinning technique to fabricate hierarchically porous graphene fibers. Through this approach, GO serves dual functions as both a dispersant for hydrogel fragments and a binder for enhancing inter-fragment connections, enabling precise control over the formation of multi-scale porous architectures while preserving high specific surface area (96.1 m² g⁻¹). The as-fabricated fiber-based supercapacitor exhibits superior electrochemical performances, achieving a volumetric capacitance of 36.5 F cm⁻³ at 0.05 A cm⁻³, coupled with exceptional rate capability (maintaining 19.6 F cm⁻³ at 10 A cm⁻³) and remarkable cycling stability. The device also demonstrates outstanding mechanical durability, maintaining 95.1 % of their initial capacitance after 20,000 bending cycles. Significantly, comprehensive scalability studies reveal that the fiber supercapacitors maintain consistent electrochemical characteristics as their length increases from 1 to 100 cm, with a stable linear capacitance of 21.1 mF cm⁻¹ at 100 cm length. These findings establish a promising pathway for the industrial-scale production of high-performance graphene fiber-based supercapacitors for next-generation wearable electronics.