First-Principles Study of Molybdenum Chalcogenide Halide Nanowires for Mg-Ion Battery Cathode Application

Two categories of molybdenum chalcogenide halide nanowires (NWs), (1) Mo 6 Ch 6– x Ha x, Ch = S or Se, Ha = I, where the unit cell consists of Mo octahedra directly linked together, and (2) Mo 12 Ch 18– x Ha x, where the unit cell consists of two Mo octahedra linked by bridging atoms, were investigated for their performance as cathode materials for Mg-ion battery. Using density functional theory calculations, we found that Mg adsorbs most strongly on pure selenium-based NWs (i.e., Mo 6 Se 6 and Mo 12 Se 18 ), with adsorption sites around the bridging atoms of Mo 12 Se 18 having the most exothermic Mg adsorption energies. We revealed that differences in Mg adsorption energy result from interactions between Mg and Mo 6 Ch 6– x I x that are antibonding (unstable), whereas the interactions between Mg and Mo 12 Ch 18– x I x are bonding (stable). In addition, we calculated the Mg diffusion barriers and specific capacities of the selenium-based NWs and compared them with other state-of-the-art cathode materials. Our results indicate that Mo 6 Se 6 NWs could potentially be used as cathode materials for Mg-ion batteries due to their low Mg diffusion barrier.