The functionalization of carbon nanofibers by using ionic liquids

Centrifugal spinning is a promising technique to design nanostructured electrodes with tunable morphology and structure. Carbon nanofibers are commonly used as anodes for sodium ion batteries (SIBs) and supercapacitors owing to high electrical conductivity, high porosity and large interlayer spacing. Herein, a facile and low-cost strategy is presented to fabricate carbon nanofibers via a fast and safe centrifugal spinning and heat treatment. Moreover, triple doping was employed by using ionic liquids to further improve electrochemical properties of carbon nanofiber electrodes for SIBs and supercapacitors. The morphology of triple doped carbon nanofibers (TDCNFs) were studied by using scanning electron microscopy (SEM) and tunneling electron microscopy (TEM). Heteroatom doping was seen from SEM EDX images. Larger interlayer spacing was observed from XRD pattern of TDCNFs. Self-standing, binder free TDCNF electrodes delivered the high reversible capacity of over 350 mAh/g at 100 mA/g with excellent cycling stability in 200 cycles compared to that of CNF electrodes (150 mAh/g). TDCNFs were also used in two-electrode supercapacitors and high capacitance of around 225 F/g was observed with excellent capacitance retention in 10,000 cycles. This work reports a promising way to prepare carbon nanofibers with tunable morphology and various compositions which could be applicable for different energy storage applications.