The search for new energy storage technologies to promote electromobility and reduce global warming is one of the greatest challenges of our time. Magnesium-ion batteries (MIB) are attracting increasing attention as an alternative to conventional lithium-ion batteries (LIB) due to the unique properties of magnesium (Mg) metal anodes, such as high volumetric capacity, low cost, and safe operation. However, mass market adoption of MIBs is currently hindered by significant challenges. One of the biggest challenges is the formation of a passivating interface on the Mg surface which is impermeable to Mg cations and leads to battery failure. Sun et al. have identified three reasons for Mg degradation in a recent review article. First, Mg has a higher charge density due to its bi-valency which leads not only to stronger coordination with solvent molecules and salt anions but also facilitates solvent decomposition at the anode. For example, Lu et al. have shown that the salt anion ClO 4 is chemically reduced at the Mg anode in carbonate-containing solvents, forming a solid-electrolyte interface (SEI) consisting of Mg-halides, MgO, Mg(OH) 2 , MgCO 3 , and Mg(ROCO 2 ) 2 . Second, short circuits are induced by non-uniform Mg growth, which can be further subdivided into hemispherical, 12 porous 13 or dendritic growth morphologies. Hemispherical 3D particles with different shapes have been detected in TFSI-based electrolytes as a function of the applied current density. In an Mg(TFSI) 2 salt electrolyte with MgCl 2 as additive, continuous stripping and plating leads to fracturing and reformation of the SEI layer, resulting in large effective current densities at the respective fracture sites and inhomogeneous Mg deposition. Through this mechanism, hemispherical deposits are further degraded to porous morphologies and trapped sediments that are irreversibly lost for cycling. The most extreme form of non-uniform Mg growth is the formation of dendrites, which occurs much less frequently at the Mg anode than in the Li equivalent. So far, dendrites have been detected only for a 0.5 M solution of MeMgCl in THF at a current density of 0.921 mA cm -2 . Third, corrosion of the Mg surface upon contact with ambient air leads to the formation of inorganic compounds such as MgO and Mg(OH) 2 at the interface. During fabrication, transport, or storage of the Mg anode, contact with impurities such as O 2 or H 2 O can hardly be avoided. In addition, traces of water in the electrolytes or oxygen residues under inert gas conditions can also lead to passivation. According to Connell et al., impurities contribute even more to passivation than decomposition products of electrolytes. To study in detail the initial steps of the Mg anode passivation by oxygen impurities, we apply the ReaxFF reactive force field method, which has proven valuable for studying battery materials. For example, Islam et al. developed a ReaxFF potential for amorphous sulfur cathodes, allowing the group to model the volume expansion and associated strain hardening during lithiation. In addition, Islam et al. studied reductive decomposition pathways of ethylene carbonate (EC) using the eReaxFF method, which can explicitly describe electrons in a pseudoclassical manner. The study demonstrated electron transfer from Li to EC to trigger ring-opening to form the Li + /EC -radical, and predicted possible radical termination products which were also detected experimentally. O'Hearn et al. trained a force field for Li/O systems with the goal of improving the description of brittle fractures in Li 2 O slabs.