Synthesis of superior carbon nanofibers with large aspect ratio and tunable porosity for electrochemical energy storage

Porous carbon nanofibers (CNFs) are regarded as essential components of high-performance energy storage devices in the development of renewable and sustainable resources, due to their high surface areas, tunable structures, and good conductivities. Herein, we report new synthesis methods and applications of two types of porous carbon nanofibers, i.e., colloidal mesoporous carbon nanofibers as electrode materials for supercapacitors, and microporous carbon nanofibers as substrate media for lithium–sulfur (Li-S) batteries. These carbon nanofibers can be synthesized either by confined nanospace pyrolysis or conventional pyrolysis of their polymeric precursors. The supercapacitor electrodes which are fabricated via a simple dipping and rinsing approach exhibit a reversible specific capacitance of 206 F g−1 at the current density of 5 A g−1 in 6.0 mol L−1 aqueous KOH electrolyte. Meanwhile, the Li-S batteries composed of microporous carbon nanofiber-encapsulated sulfur structures exhibit unprecedented electrochemical performance with high specific capacity and good cycling stability, i.e., 950 mA h g−1 after 50 cycles of charge–discharge. The excellent electrochemical performance of CNFs is attributed to their high-quality fiber morphology, controlled porous structure, large surface area, and good electrical conductivity. The results show that the carbon nanofibers represent an alternative promising candidate for an efficient electrode material for energy storage and conversion.