A Comparative Study of 2D MoSe ₂ /NbX ₂ (X = S, Se) vdW Heterostructures as Anode Materials for Sodium‐Ion Battery: A First‐Principles Calculations

This study investigates two‐dimensional (2D) MoSe ₂ /NbX ₂ (X = S, Se) van der Waals heterostructures as anode materials for sodium‐ion batteries using density functional theory. It focuses on how the chalcogen atom in NbX ₂ affects structural, electronic, and electrochemical properties. Both MoSe ₂ /NbS ₂ and MoSe ₂ /NbSe ₂ are energetically stable with low‐strain configurations and binding energies of –125.60 and –130.07 meV per unit cell. Both systems exhibit metallic behavior, favorable for charge transport. Sodium adsorption is stronger in MoSe ₂ /NbS ₂ (–1.83 eV) than in MoSe ₂ /NbSe ₂ (–1.01 eV). Accordingly, MoSe ₂ /NbS ₂ shows a higher storage capacity (188 mAh/g) and lower open‐circuit voltage (0.35 V) than MoSe ₂ /NbSe ₂ (106 mAh/g, 0.87 V), both within the desirable range. Simulations confirm thermal stability at 300 K, while CI‐NEB results indicate faster Na‐ion diffusion in MoSe ₂ /NbS ₂ . The superior performance of MoSe ₂ /NbS ₂ is attributed to a larger work function difference, generating a stronger interfacial electric field that enhances sodium adsorption and diffusion. Overall, chalcogen selection in NbX ₂ offers an effective strategy for optimizing 2D heterostructure anodes.