A computational study on the potential application of zigzag carbon nanotubes in Mg-ion batteries

Abstract

Although Li-ion batteries are extensively applied for different purposes, they suffer from safety problems, high cost, and short lifetime. Because of low cost, wide availability, and nontoxicity of magnesium, Mg-ion batteries (MIB) might be a good alternative to Li-ion batteries. Here, applying density functional theory calculations, we examined the potential application of zigzag (4,0), (5,0), (6,0), (7,0), and (8,0) carbon nanotubes in the anode of MIBs. We found that by increasing the tube diameter, the Mg2+ adsorption energies are very slightly changed but the Mg adsorption sharply decreased indicating that the adsorption of Mg atom much more depends on the tube diameter and its adsorption energy is the key parameter for generating a cell voltage. We showed that by increasing the curvature of the CNT, the charge transfer is sharply increased upon Mg atom so that in the highest curvature, the interaction becomes ionic in nature with a Jahn-Teller distortion in the CNT structure. However, by increasing the CNT diameter, the cell voltage of MIB increased, from 4.0 V in the (4,0) to 5.3 V in the (8,0) CNT.