Graphene induced N/O doping and structural regulation of carbon nanofibers for enhanced sodium storage

The addition of carbon nanotubes (CNTs) and graphene (G) to nitrogen-doped carbon nanofibers (N-C/CNFs) greatly improves their performance as sodium ion battery anodes. However, there is currently limited research on whether the introduction of nanocarbon materials will affect the surface functional groups, defects, and material structure. Herein, the classical G and CNT were introduced into the N-C/CNFs. And the addition of G promotes the transformation of nitrogen-containing functional groups (NFGs), resulting in a substantial pore structure and an enlarged interlayer distance, which enhances the macroscopic electrochemical performance significantly. The nitrogen-doped graphene/carbon composite nanofibers (N-G/CNFs) exhibit superior electrochemical performance compared to N-C/CNFs and nitrogen-doped carbon nanotube/carbon composite nanofibers (N-CNT/CNFs). After 200 cycles, the N-G/CNFs demonstrate a reversible capacity of 295 mA h g-1 at 0.05 A g-1, significantly higher than the capacities of N-C/CNFs (193 mA h g-1) and N-CNT/CNFs (237 mA h g-1). The Na3V2(PO4)3@C//N-G/CNFs exhibit promising energy and power densities. Nitrogen-doped carbon/carbon composite nanofibers have expanded layer spacing, abundant surface functional groups and a rich pore structure to store Na+, resulting in excellent electrochemical performance.