A Comparative Study of 2D MoSe2/NbX2 (X = S, Se) vdW Heterostructures as Anode Materials for Sodium-Ion Battery: A First-Principles Calculations Approach

Abstract

This study investigates two-dimensional (2D) MoSe₂/NbX₂ (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 NbX₂ affects structural, electronic, and electrochemical properties. Both MoSe₂/NbS₂ and MoSe₂/NbSe₂ 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 MoSe₂/NbS₂ (–1.83 eV) than in MoSe₂/NbSe₂ (–1.01 eV). Accordingly, MoSe₂/NbS₂ shows a higher storage capacity (188 mAh/g) and lower open-circuit voltage (0.35 V) than MoSe₂/NbSe₂ (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 MoSe₂/NbS₂. The superior performance of MoSe₂/NbS₂ is attributed to a larger work function difference, generating a stronger interfacial electric field that enhances sodium adsorption and diffusion. Overall, chalcogen selection in NbX₂ offers an effective strategy for optimizing 2D heterostructure anodes.