This study systematically investigates the adsorption behavior of sodium atoms on zigzag (7,0) and armchair (7,7) carbon nanotubes (CNTs) using first-principles calculations, focusing on their effects on the electronic structure and optical properties. Three adsorption configurations—inner, outer, and double-sided—were analyzed to clarify the mechanisms of charge transfer and orbital hybridization. The results indicate that internal adsorption in zigzag (7,0) CNTs (−9.43 eV) and external adsorption in armchair (7,7) CNTs (−8.16 eV) achieve a favorable balance between adsorption stability and desorption reversibility, with adsorption energies and diffusion barriers that are more consistent with practical requirements. Optical analyses show typical Drude-type conductive behavior and pronounced polarization in both systems, with the double-sided structure displaying the strongest dielectric and optical conductivity responses. These findings provide valuable theoretical guidance for the design and optimization of carbon-based sodium-ion battery electrodes.
Yin et al. (Sat,) studied this question.