Zigzag And Armchair Aln Nanotubes As Anode Materials For Mg-Ion Batteries: Computational Study

We studied the potential application of a zigzag and an armchair AlN nanotube (AlNNT) as an anode material for the Mg-ion batteries (MIBs) using B3LYP-gCP-D3/6-31G* model chemistry. The Mg2+ adsorption energy on the zigzag or armchair AlNNTs is -217.2 or -234.9 kcal/mol, but the Mg atom interaction is much weaker and the adsorption energy is -10.5 or -5.3 kcal/mol. The dispersion term is much more important for the Mg interaction compared to the Mg2+. This term includes 68.6% of the Mg atom adsorption energy on the zigzag tube while its contribution for Mg cation adsorption is about 3.8%. The maximum energy barrier for an Mg2+ migration and cell voltage are 6.1 kcal/mol and 4.47 V for zigzag and 5.3 kcal/mol and 4.95 V for armchair AlNNT, respectively. Thus, the AlNNTs provide a great ion mobility leading to a faster charge/discharge rate because of small energy barriers. The larger cell voltage, and higher ion mobility suggest the armchair AlNNTs as a plausible anode material for application in the anode of MIBs, compared to the zigzag AlNNT. The effect of Mg/Mg2+ adsorption on the electronic properties of AlNNTs is also discussed.