Advanced core-shell hollow carbon nanofibers for ion and electron accessibility in sodium ion batteries.

One-dimensional core-shell hollow carbon nanofibers (HCNFs) have been synthesized by coaxial electrospinning, deacetylation and carbonization, which exhibit multi-surface properties that enhance electrolyte infiltration and facilitate ion/electron transport. The nitrogen-doped hard carbon outer shell compensates for the low conductivity of amorphous carbon, and the inner core carbon supports the stability of core-shell hollow structures. This unique structure ensures the accessibility of electrons/ions during electrochemical reactions and contributes to the superior rate performance of HCNFs. Ultimately, a high retention rate of 77% of the initial capacity value (0.1 A g -1 ) was demonstrated at a current density of 2 A g -1 . The core-shell hollow structure designed in this work greatly optimizes the sodium transport dynamics.