Nitrogen-enriched carbon nanofibers with tunable semi-ionic C[sbnd]F bonds as a stable long cycle anode for sodium-ion batteries.

• The modified electrospun fibers with semi-ionic C F bond was prepared by CF 4 plasma. • The semi-ionic C F bond benefit to the fast ion and electron transfer for electrode. • Rate performance and long cycles of anode depend on the content of semi-ionic C F bond. • F doped N -enriched fibers deliver long term capacity with 150 mA h g−1 over 2000 cycles. 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 C F bonds decorating nitrogen-enriched electrospinning carbon nanofibers (NCNFs) as a free-standing anode for NIBs. The semi-ionic C F 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−1 at 0.1 A g−1 and displays excellent long-term stability with reversible specific capacity around 150 mA h g−1 over 2000 cycles at 500 mA g−1 after the rate capability test. Moreover, the presence of semi-ionic C F 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. [ABSTRACT FROM AUTHOR]