Intercalation mechanism of solvated magnesium electrolytes on spinel cathode surfaces

Multivalent magnesium ions have significant potential in energy storage systems beyond lithium ions. The advancement of magnesium battery technologies relies on the discovery of suitable battery materials and understanding their interfacial reaction mechanisms. Nonetheless, the impact of the cathode surface on the desolvation and intercalation mechanisms of solvated magnesium electrolytes remains uncertain. In this study, using first-principles calculations, we find how different surface conditions affect the desolvation and intercalation of solvated magnesium electrolytes on MgV₂O₄ cathodes. Magnesiated cathodes enhance the kinetics of magnesium electrolyte desolvation and intercalation compared to demagnesiated cathodes. Intercalation is more favorable than deintercalation on magnesiated cathodes, while the opposite is favorable for demagnesiated cathodes. The presence of surface water molecules significantly reduces overall activation energy. The (001) surface orientation exhibits lower activation barriers than the (111) orientation, with crystallography affecting diffusivity. Chromium doping decreases activation energies for desolvation and intercalation under the magnesiated condition but increases them in the demagnesiated condition. Our findings yield comprehensive insights into the importance of cathode surface design in Mg batteries, and these insights contribute to the progress and development of battery technologies, offering significant implications for advancements in energy storage.