Physical Forces Inducing Thin Amorphous Carbon Nanotubes Derived from Polymer Nanotube/SiO₂ Hybrids with Superior...

Different from the traditional template method, a thin amorphous carbon nanotube was prepared by constructing a polymer/SiO₂ composite, utilizing the shrinking action of sulfonated polymer nanotubes (SPNTs) and the physical squeezing action of SiO₂ on it during the pyrolysis of SPNT/SiO₂. Remarkably, the heat treatment atmosphere (N₂, N₂-H₂, or O₂) has an important effect on the surface properties, pore structure, crystallinity, and especially the defect sites, leading to different lithium storage performances. Particularly, the sample calcined in N₂-H₂ (NHCNTs) exhibits outstanding reversible capacity (400.6 mA h g^-1 at 2 A g^-1 after 200 cycles) and rate capability (268.4 mA h g^-1 at 5 A g^-1 and 212.1 mA h g^-1 at 10 A g^-1 after 400 cycles), which are attributed to the thin-walled tubular structure and abundant defect sites. NOCNTs can be obtained by the thermal treatment of NCNTs (the sample of polymer pyrolysis in N₂) in air, and the oxygen content was increased. However, the destruction of the tubular structure led to poor electrochemical properties. These results proved the importance of the thin-walled tubular structure to the electrochemical properties. Surely, this strategy for preparing thin-walled carbon nanotubes can be widely extended to the preparation of other nanomaterials with thin-walled structures.