Solvent–Anion Counterpoised Electrolyte Enables High‐Rate Magnesium Metal Batteries

Abstract

ABSTRACT Magnesium batteries are compelling post‐lithium energy storage candidates but suffer from sluggish charge transfer kinetics, fundamentally restricted by the high energy barrier of Mg 2+ desolvation. Herein, we address the compact and tenacious solvation sheath induced by the high charge density of Mg 2+ , characterized by strong electrostatic binding. To effectively weaken the coordination strength and lower the desolvation barrier, we utilize machine learning to identify electrolytes that energetically balance Mg 2+ ‐solvent and Mg 2+ ‐anion interactions. This counterpoise state leads to a comprehensive weakening of the solvation shell. As corroborated by in situ Raman spectroscopy, this environment facilitates a synchronous desolvation pathway and induces a robust MgH 2 ‐based solid‐electrolyte interphase, fundamentally accelerating interfacial kinetics. The screened amine‐based electrolyte empowers low‐overpotential Mg 2+ reduction of 0.06 V at 1 mA cm −2 , and full cells with high‐rate performance sustain 50 C cycling, and a Mg/fluorinated carbon cell delivers 918 mAh g −1 at 0.5 C. This paradigm shifts the design focus from individual solvation to collective energy equilibration in multivalent electrolytes.