Theoretical investigation of halides encapsulated Na@B₄₀ nanocages for potential applications as anodes for sodium ion batteries

The increasing demand of energy storage materials has attracted considerable attention of scientific community towards the development of rechargeable ion batteries (RIBs). Herein, B₄₀ nanoclusters are theoretically analyzed for their potential application as anode material for sodium-ion batteries. DFT calculations are performed for geometrical and electrochemical properties study of Na or Na⁺ adsorbed A⁻@B₄₀ (A⁻ = F^-, Cl^- and Br^-) complexes. Na⁺ and Na adsorbed preferably on R₇ and R₆ positions of boron nanocage (B₄₀), respectively, where the interaction of Na⁺ is stronger in comparison to Na atom. The change in Gibbs free energy (cell potential) values of R₇-B₄₀ and R₆-B₄₀ complexes (of bare case) are −11.21 kcal mol⁻¹ (0.49 V) and −8.92 kcal mol⁻¹ (0.39 V), respectively. For further improvement of change in ΔG and V_cell values, halides are encapsulated (A = F^-, Cl^- and Br^-) into boron nanocage. The V_cell of Na-ion batteries for R₇-A@B₄₀ and R₆-A@ B₄₀ (A = F^-, Cl^- and Br^-) increases up to 3.594 V and 3.492 V, respectively. These results illustrate that the electrochemical properties of A@B₄₀ nanocage explicitly depend on the nature of alkali metals and their respective halide ions.