Ab-initio investigation of lithium adsorption on short carbon nanotubes considering effects of the tube length

Abstract

Carbon nanotubes (CNTs) are a candidate electrode material for lithium-ion batteries (LIBs). Tailoring CNTs to shorter tubes with open ends can enhance the lithium capacity. Recently, the carbon nanobelt (CNB) has been successfully synthesized. This work concentrates on ab initio modelling of lithium adsorption on short open-ended CNTs with different lengths based on density functional theory (DFT). Li atoms adsorbed on CNB (one-segment (6,6) CNT) and short (6,6) CNTs with 2–12 segments as well as periodical CNTs were modelled. The most stable Li-CNT configurations were obtained after the total system energies were minimized. Lithium adsorption energies of short CNTs were found to have a regular oscillatory dependence on the number of segments along tube axis. Energetics for lithium moving across the tube wall and along the tube axis were also calculated for open-ended CNTs. Ab initio molecular dynamics (ABMD) was performed to simulate the lithium diffusion behaviors in short CNTs. Among all short CNTs, the CNT with 2 segments was the most promising electrode material for LIBs and its lithium capacity was finally predicted.