Coinage Metal Doping Engineering of Monolayer MoS2 for Magnesium-Ion Battery Anodes: A First-Principles Study

Magnesium-ion batteries have attracted extensive attention due to their abundance, high safety, and superior volumetric energy density. However, their development remains constrained by the sluggish diffusion of Mg2+ ions and the limited magnesium storage capacity of electrode materials. In this work, we systematically investigate the Mg storage performance and underlying mechanisms of monolayer MoS2 anodes substitutionally doped with Cu, Ag, and Au at a concentration of 4% on the Mo sublattice. The results reveal that all three dopants maintain the structural integrity of the two-dimensional MoS2 framework after optimization while introducing localized electronic states near the Fermi level, thereby enhancing Mg adsorption. Compared with intrinsic MoS2, the doped systems exhibit markedly improved Mg binding. Sequential adsorption calculations indicate that, at the investigated 4% substitution concentration, Cu-MoS2, Ag-MoS2, and Au-MoS2 can stably accommodate up to five Mg atoms, elevating the theoretical specific capacity to ~67 mAh/g while maintaining low open-circuit voltages during magnesium intercalation. Diffusion kinetics analysis further shows that Cu-MoS2 possesses the lowest Mg migration barrier (0.25 eV), surpassing Ag-MoS2 (0.38 eV) and Au-MoS2 (0.61 eV). Considering both thermodynamic stability and ion transport kinetics, Cu-MoS2 achieves an optimal balance among storage capacity, operating voltage, and diffusion performance, highlighting its promise as a high-performance anode material for magnesium-ion batteries.