Imidazole-Amine Synergistic Coordination Reconstructs H-Bonds and Interface Engineering for Mg Metal Batteries at 60°C.

Rechargeable magnesium batteries (RMBs) are greatly hindered by critical issues in ether and ether-nitrogen co-solvent electrolytes, such as Mg anode passivation, large overpotential, poor thermal stability, and flammability. Herein, we design a deep eutectic electrolyte (DEE, DMSA) consisting of dimethylimidazole (DMIm), Mg(TFSI)2, and 2-methoxyethylamine (MEA) in a molar ratio of 16:1:3. The dual role of the MEA additive synergistically involves the cleavage of the excessively strong DMIm-Mg2 + solvation structure and the reconfiguration of the robust DMIm-TFSI- hydrogen-bonding network. Through imidazole-amine coordination competition and a synergistic hydrogen-bonding network, the solvation structure is reconstructed with a reduced Mg desolvation barrier. Meanwhile, the in situ MgF2-rich organic/inorganic bilayered SEI ensures the interfacial stability and cycling lifespan. In particular, the inorganic layer portion of MgF2-rich, effectively enhances the stability of the SEI layer at high temperatures. The optimal DEE features intrinsic flame retardancy, a broad operating temperature range (10-80°C), and an ultra-low overpotential of 35 mV. Astoundingly, the Mg||Mg cell runs stably for 400 h at 80°C. Impressively, the Mg||Mo6S8 cell realizes long cycling over 1000 cycles even at 5 C at 25°C and 150 cycles at 60°C. This work establishes a new solvation design principle that fundamentally resolves the long-standing incompatibility between Mg and non-aqueous eutectic electrolytes, unlocking high-performance, high-temperature RMBs.