The effect of structural curvature on the cell voltage of BN nanotube based Na-ion batteries

Nanotube-based ion batteries have fascinated the researchers due to high cyclability, high capacity, and high energy density of nanotubes. Here, the application of BN nanotubes (BNNTs) and BN nanosheets in Na-ion batteries are explored using density functional theory calculations. Investigating the interaction of both Na and Na+ with different BNNTs and BN nanosheet, we demonstrated that the cell voltage of Na-ion batteries increase by decreasing the structural curvature of the BN structures. Calculated cell voltage for the small (5, 0) BNNT and the BN nanosheet is about 1.12 and 1.55 V, respectively. The interaction of atomic Na with the surface of the BN structures plays the main rule in determining the cell voltage. Also, our calculations indicate that the aromaticity and hybridization of the atoms of BN structures affect the performance of Na-ion batteries. Based on the results, it can be understood that why the disk like BN sheets are more suitable than BNNTs for application in the anode electrode of Na-ion batteries.