Sodium ion battery anode properties of empty and C60-inserted single-walled carbon nanotubes

The structural changes of three different Single-Walled Carbon Nanotube (SWCNT) samples (open- and closed-end, and C-60-peapod SWCNT samples) with Na doping were investigated by Raman scattering and XRD measurements. It was found that the sodium atoms are inserted into the nanotube hollow core space in the case of open-end SWCNTs. The Na ion battery anode properties of the three samples were also investigated by electrochemical measurements. These results show that the space inside the SWCNTs cannot function electrochemically as sodium ion adsorption sites. However, it was found that the reversible sodium ion storage capacity of the C-60-peapod sample is much larger than that of an empty tube.