Nitrogen-enriched carbon nanofibers with tunable semi-ionic CF bonds as a stable long cycle anode for sodium-ion batteries.

The quest for getting more efficient carbonous anodes for sodium ion batteries (NIBs) prepared by simple and economical methods continues to be an important endeavor. Herein, a plasma-controlled method is developed for preparing semi-ionic CF bonds decorating nitrogen-enriched electrospinning carbon nanofibers (NCNFs) as a free-standing anode for NIBs. The semi-ionic CF bonds are beneficial to the fast ion and electron transfer for a free-standing electrode, which remarkably improves the rate performances of NCNFs as the NIBs anodes. The optimized sample delivers a reversible capacity of 199 mA h g at 0.1 A g and displays excellent long-term stability with reversible specific capacity around 150 mA h g over 2000 cycles at 500 mA g after the rate capability test. Moreover, the presence of semi-ionic CF bonds on plasma nitrogen-enriched electrospinning carbon nanofibers surfaces can reduce the resistance of the anode, thereby showing a more stable solid electrolyte interphase SEI) after electrochemical cycles.