Unveiling the energy storage potential of Janus YSSe, ZrSSe and NbSSe monolayers as anode materials for Mg-ion batteries: DFT and AIMD insights.

In the rapidly developing domain of energy storage, magnesium-ion batteries (MIBs) provide an attractive, cost-effective and potentially high-performance alternative to conventional lithium-ion batteries. We systematically explore YSSe, ZrSSe and NbSSe monolayers as promising host candidates for MIBs using density functional theory. The unique atomic configuration of these nanosheets exhibits significant stability, as validated by cohesive energy, formation energy, phonon dispersion, AIMD simulation, vibrational analysis and Gibbs free energy studies. This study reveals the electronic properties of the pristine nanosheets, among which YSSe and NbSSe display metallic attributes, while ZrSSe has a semiconducting bandgap of 1.33 eV (HSE06). Upon magnesiation, all the nanosheets undergo transition to metallic states, which indicates that during the charging process, electrons are transported efficiently. The computed diffusion barrier of Mg ions indicates that diffusion at the Se site is more favorable compared with that at the S site, and NbSSe shows the lowest migration barrier (0.61 eV). Without structural deformation, all three nanosheets can accommodate the maximum number of Mg atoms, and the theoretical specific capacities are 953.368, 942.341 and 759.337 mAh g