Exploring the anodic performance of ScSeS and TiSeS monolayers of modified transition metal dichalcogenides for Mg ion batteries via DFT calculations.

Abstract

Due to the significant ambient abundance of magnesium metal and the divalent nature of the magnesium ion, rechargeable magnesium-ion batteries are a strong candidate to fulfill the forthcoming demands for electrical energy storage in both extensive mobile and stationary applications. Transition metal dichalcogenides (TMDs) are still regarded as newcomers within the realm of 2D nanomaterials, particularly in the context of their applications in energy storage. Here, we report a DFT-based analysis on TMDs as anode materials in Mg ion batteries using the GGA-PBE exchange-correlation functional. This study investigates the structural, electronic and adsorption behavior of ScSeS and TiSeS nanosheets. All predicted TMDs adsorbed Mg-atoms with favorable adsorption energy (Eads) without any noticeable structural distortion, exhibiting good structural stability. For three distinct adsorption sites, top of the transition metal (Sc, Ti), Se and S, the Eads are calculated as -3.74 eV, -3.62 eV, -3.40 eV and -1.23 eV, -1.38 eV, -0.91 eV, which indicates that Eads is higher when the Mg ion is adsorbed at the Sc and Se atomic sites, respectively. The Eads for ScSeS are almost two times the Eads for TiSeS. In the band structure, it is seen that for both ScSeS and TiSeS, the conduction band crosses the Fermi level, which implies the metallic behavior of the nanosheets. Furthermore, they show a maximum theoretical specific capacity of about 686.18 mA h g-1 and 546.63 mA h g-1, which is almost two times higher than that of the bulk graphite anode material. The average open circuit voltages are calculated as 0.43 V and 0.11 V for ScSeS and TiSeS, respectively.