Chemical defects as Li⁺ ion traps: a theoretical study

We investigate how sp³ quantum defects on single-walled carbon nanotubes act as atomic-scale traps for individual lithium ions. Density functional theory (DFT) calculations show that endohedrally incorporated Li⁺ in (7,5) single-walled carbon nanotubes preferentially localize near aryl-hydroxyl sp³ defects, with a binding energy of ∼2.95 eV. This defect-ion interaction redistributes local charge, perturbs frontier orbitals, and produces a 437 meV red-shift in the defect absorption spectrum, as revealed by time-dependent DFT. These findings highlight the sensitivity of quantum defects to ions, with implications for ion detection, quantum emitters, and lithium storage in carbon nanotube-based electrodes.