Electrochemical properties of stanene as an efficient anode material for Na-ion batteries

Abstract

We address the suitability of two dimensional (2D) mono layer of tin for anode material of Na-ion batteries (NIBs), within the framework of density functional theory (DFT). The cohesive energy for the three possible structures (planar, buckled and puckered) of stanene have been calculated. Present calculations suggest that hollow (H) site is most favorable for Na adsorption. The optimized distance in perpendicular direction for Na adsorption at H site is 1.68 Å. However at top, bridge and valley sites it comes equal to 2.90, 2.55 and 3.04 Å, respectively. The adsorption energy has been computed for different number (n) of adsorbed Na atoms on stanene. The Bader charge analysis indicates that each Na loses 0.77 e¯ per atom electronic charge to Sn atoms of stanene. During the sodiation process, there is minor distortion in lattice vectors with respect to pristine stanene. We have also calculated the average intercalation voltage (AIV) for different values of n. To study diffusion of Na on stanene, the most reliable climbing image nudged elastic band (CI-NEB) method based calculations have been carried out, which provides energy barrier of Na diffusion between the two initial guess states.