First-principles study of Li adsorption in a carbon nanotube-fullerene hybrid system Original Research Article

A carbon hybrid material system consisting of single wall carbon nanotubes (SWCNTs) and fullerene (C60) has been investigated using the first-principles methods. Through combining metallic SWCNTs with C60 of high electron affinity, the lithium adsorption energy on this CNT-C60 hybrid system (−2.110 eV) is found to be larger than that of the pure SWCNTs (−1.720 eV). By characterizing the electronic properties of the CNT-C60 system such as band structure, density of states and charge distribution as a function of the Li adsorption in comparison with SWCNT or C60, it is also found that the Li adsorption takes place on the C60 side preferably due to the large adsorption energy, which imparts metallic character to the C60 in the CNT-C60 hybrid system. Investigating various adsorption sites on the CNT-C60 system in order to understand the adsorption mechanism of Li, it is found that Li atoms are preferably adsorbed at every other hexagonal or pentagonal site (next nearest neighboring sites) rather than every site (nearest neighboring sites) on the hybrid system. The possibility of Li cluster formation in this CNT-C60 system does not seem to be high since the Li–Li binding is less favorable than the Li adsorption on the CNT-C60 system.