Density Functional Study of Interaction of Lithium with Pristine and Stone-Wales-Defective Single-Walled Silicon Carbide Nanotubes

Interactions between a lithium atom or a lithium ion with pristine and Stone-Wales-defective (SW-defective) (5, 5) single-walled silicon carbide nanotubes (SiCNTs) were studied using density functional theory (DFT) with truncated nanotube models. The results show that the lithium atom or ion prefers to interact with defective SiCNTs, although the increase of binding energy for Li+ bonding with SiCNT is much smaller than that of the Li atom bonding with SiCNT. The molecular orbital energy level splits after a defect is created on the SiCNT, and along with localization of charge-electron density on the defect, it results in binding lithium more efficiently. Lithium always remains positively charged, irrespective of their charge state (neutral or cation) or the different rings that it interacts with. In addition, we also explore the possibilities of Li+ intercalation through the side-wall of SiCNT by examining the energy barrier. It is found that the barrier to insertion of Li+ through the ring of SiCNT depends on the ring size. The energy barrier of Li+ moving through the hexagon ring of perfect SiCNT was 7.02 eV, whereas it dropped to 2.5 eV when Li+ moved through the heptagon ring of the SW-defective SiCNT.