Li-insertion into carbon nanotubes: Experiment and theory

Lithium-insertion during the arc discharge growth process is investigated by using resonance Raman spectroscopy combined with ab initio calculations. The measurements were performed using two pairs of single-wall carbon nanotubes, one of the members being prepared employing a lithium-contained catalyst and the other its lacking lithium counterpart. The lowest wave number lines were observed as selective resonances for the first pair for which a line occurs at 142.3 cm−1 from the Li-catalyst prepared sample and at 162.2 cm−1 for the non-lithium case. The remaining lines are seen in both samples. For the second pair the first two lower-lying lines are selectively seen for the non-lithium sample while for the lithium-contained catalyst case the two highest wave number lines are selectively observed. These different resonance conditions lead us to perform electronic property calculations. The results show that this effect can be tracked to the charge transfer occurring from lithium atoms inserted into the bundles. Calculation shows that the transfer is limited to a Li-insertion rate of Li6C68.