Solute–Solvent Dual Engineering Enables the Fluorinated Interface of the Mg Anode for Sustainable Aqueous Magnesium Batteries

Rechargeable aqueous magnesium batteries (RAMBs) offer unparalleled advantages, particularly in environmental sustainability, safety, and cost-effectiveness. However, the practical implementation of RAMBs in aqueous electrolytes has been critically hampered by the passivating nature of Mg. In this work, the aqueous cosolvent electrolyte spontaneously induces the formation of a protective interfacial film on the Mg anode via in situ chemical reactions, driven by the solute–solvent dual engineering strategy. This innovative approach effectively mitigates Mg anode passivation while enabling reversible Mg plating/stripping processes in aqueous electrolytes, as evidenced by stable electrochemical performance metrics including minimal overpotential (0.31 V) over 600 h of Mg||Mg symmetric cells. The PTO||Mg full cell exhibits a well-maintained discharge plateau at 1.25 V and a discharging capacity of 138 mAh g–1 in 0.1–2.2 V. This result highlights the feasibility to stabilize the Mg anode by interfacial engineering through the cosolvent electrolyte design.