Ultrafine Carbon-Nanofiber-Reinforced Graphene Fiber Electrodes for Flexible Supercapacitors with High Specific Capacitance and Durable Cycle Stability

Graphene fiber-based supercapacitors (FSCs) are one of the most promising energy storage devices for flexible electronics. However, the electrochemical performance of conventional graphene fiber electrodes fabricated by wet spinning is still limited by the low specific surface area (SSA), mismatched pore size distribution, and considerable interface resistance. Herein, we developed a scalable method to produce hierarchical porous carbon nanofibers/graphene hybrid fibers (CNGFs) for flexible supercapacitor electrodes with high specific capacitance and durable cycle stability. For energy storage applications, both ion storage accommodation and rapid electronic transfer are required, which could be achieved by the ultrahigh SSA and exceptional conductivity of CNGF electrodes. Therefore, the electrodes of CNGF30 (hybrid fibers with 30% carbon nanofiber loading) exhibit excellent electrochemical performance in terms of the area of areal-specific capacitance (409.1 mF/cm²) and cycle stability (97.7% over 10 000 cycles). Moreover, the well-designed CNGF30 offers remarkable mechanical flexibility for assembled FSCs.