Dipole-Interaction-Tailored Solvation Structure and Interface Chemistry for B-Based Magnesium Electrolyte at High Current Density

Abstract

The development of advanced boron-based electrolytes with bulky, weakly coordinating anions is indispensable for practical magnesium rechargeable batteries. However, sluggish desolvation kinetics, insufficient rate capability, and complex synthesis procedures remain critical challenges. Herein we report a molecular engineering strategy integrating dipole interactions and interface regulation to synthesize a boron-based electrolyte (EMOB) consisting of 0.3 M 1:2 ethylmagnesium chloride (EtMgCl)/1,4-oxazinane borane (MOB) via a Lewis acid–base reaction. Notably, the Mg||Mo cell exhibits outstanding cycling stability over 1000 cycles at a high current density of 5 mA cm–2, outperforming most previously reported boron-based electrolytes. Mechanistically, the multiple dipole interactions effectively weaken Mg2+–ligand coordination, reducing the desolvation barrier and promoting rapid Mg-ion transport. Concurrently, the excess MOB facilitates the formation of a robust organic–inorganic C–N/B–N SEI film. This work highlights a synergistic design strategy of dipole interaction regulation and interfacial engineering toward long-lifespan, high-power-density electrolytes.