Characteristics of lithium adsorption near divacancy defects on carbon nanotubes (7,7)

First-principles modeling is used to study the lithium adsorption on defective single-walled carbon nanotube (SWCNT). The article considers SWCNTs (7,7) with divacancy defects (2V defect) in the model with periodic boundary conditions. Due to the use of these conditions, the article discusses the problem of proper sizing of the defective tube fragment subject to modeling. Special attention is paid to the search for stable equilibrium positions (adsorption sites) for the lithium atom interacting with the defective tube and the evaluation of the configurations with the lowest energy of these sites. It is shown that all the adsorption sites located near the defect within the first three environments of carboatomic 6-rings are more energetically favorable for adsorption than the adsorption sites on the defectless tube section. Most energetically favorable are the sites above the 8 and 5-rings forming the 2V-defect. During external adsorption, the adsorption site occurs above each 6-ring within the defect. During internal adsorption, most of the 6-rings of the first defect coordination environment cannot keep the lithium atom rolling down into the defect area. The identified regularities are of direct interest in relation to the search for perspective materials for lithium-ion batteries.