Design and performance of a multifunctional coating with magnesium-philic and hydrophobic properties on the surface of magnesium battery anodes

Magnesium metal batteries are promising for next-generation energy storage due to their high energy density and low cost. However, in aqueous electrolytes, the formation of a passivation layer on the magnesium surface—hindering ion conduction—remains a major challenge. This study proposes a two-step method to prepare a multifunctional Sn@MXene interface protective layer with strong magnesium affinity and high hydrophobicity. The Sn@MXene layer was applied to magnesium metal batteries to improve performance. Results show that its strong hydrophobicity (contact angle of 132°) prevents direct contact between the aqueous electrolyte and the magnesium anode, effectively reducing side reactions such as hydrogen evolution and corrosion. In the symmetrical cell configuration, the Sn@MXene coating effectively suppresses passivation on the magnesium surface and significantly reduces interfacial charge-transfer resistance, leading to improved cycling stability and longer discharge duration. In full cell tests, the coating greatly reduces voltage hysteresis and battery impedance while extending the discharge plateau. Long-term cycling tests further confirm its ability to enhance charge-discharge stability. DFT calculations show that Sn nanoparticles enable uniform magnesium ion deposition, while Ti₃C₂Cl₂ lowers the reaction kinetic barrier on the anode surface. This enhances both ion deposition/stripping and reaction kinetics, significantly improving the electrochemical performance of magnesium batteries.