Ultrathin Carbon Nanotubes for Efficient Energy Storage： a First-Principles Study

On the basis of first-principles density functional calculations, the present study sheds theoretical insight on ultrathin carbon nanotube （UCNT） and hydrogenated ultrathin carbon nanotube （HUCNT） for use as potential materials not only for Li-ion battery anode but also for high-capacity hydrogen storage. The highest Li storage capacities in UCNT and HUCNT can be of LiC4 and LiC4H2, respectively, which are higher than that in graphite and LiC6. Binding between Li （Ca） atoms and these materials are found to be enhanced considerably. Each Li （Ca） atom may bind multi-hydrogen molecules, and the adsorption energies are ideally suited for storing hydrogen under ambient conditions, and the predicted weight percentage of molecular hydrogen are in the range of 6.4-12 wt% exceeding the target set by the United States Department of Energy.