Mechanism of Li Adsorption On Carbon Nanotube-Fullerene Hybrid System: A First-Principles Study

The lithium (Li) adsorption mechanism on the metallic (5,5) single wall carbon nanotube (SWCNT)-fullerene (C₆₀) hybrid material system is investigated using first-principles method. It is found that the Li adsorption energy (-2.649 eV) on the CNT-C₆₀ hybrid system is lower than that on the peapod system (-1.837 eV) and the bare CNT (-1.720 eV), indicating that the Li adsorption on the CNT-C₆₀ hybrid system is more stable than on the peapod or bare CNT system. This is due to the C₆₀ of high electron affinity and the charge redistribution after mixing CNT with C₆₀. In order to estimate how efficiently Li can utilize the vast surface area of the hybrid system for increasing energy density, the Li adsorption energy is calculated as a function of the adsorption positions around the CNT-C₆₀ hybrid system. It turns out that Li preferably occupies the mid-space between C₆₀ and CNT and then wraps up the C₆₀ side and subsequently the CNT side. It is also found that the electronic properties of the CNT-C₆₀ system, such as band structure, molecular orbital and charge distribution, are influenced by the Li adsorption as a function of the number of Li atoms. From the results, it is expected that the CNT-C₆₀ hybrid system has enhanced the charge transport properties in addition to the Li adsorption, compared to both CNT and C₆₀.