Unlocking High-Voltage Cathode Compatibility of Amine-Based Solvents through Enhanced Cation–Solvent Interaction for Rechargeable Mg Batteries

Conventional amine-based electrolytes exhibit superior compatibility with Mg metal anodes, but their practical application is fundamentally constrained by both a restricted electrochemical stability window (<2.0 V on Al foils) and non-negligible high cation desolvation energy barriers. Herein, we first focus on enhancing cation-solvent interaction through a rational high-concentration Li/Mg dual-salt strategy, effectively suppressing free amine solvent molecules and thereby expanding the electrochemical window to exceed 3.0 V. This widened electrochemical window ensures direct compatibility with the industrial Li-ion cathode. Furthermore, to address the high cation desolvation energy barriers and low conductivity in this electrolyte, the ether solvent with a lower coordination ability is introduced into the electrolyte, where part of the ether can participate in the Li⁺ solvation structure to alleviate overly strong amine coordination, while the rest can serve as a pseudo-diluent, promoting a reduced cathode desolvation energy barrier and enhanced ion transport. Finally, the Mg//LiFePO₄ battery delivers a stable plateau of 2.7 V and a high energy density at the electrode level. This work proposes an efficient electrolyte design paradigm that simultaneously balances Mg anode reversibility, high-voltage cathode compatibility, and a facile preparation method in Mg batteries for the first time, revealing a comprehensive exploration process for high-voltage Mg batteries.