Descriptor‐Informed Screening of Interface‐Active Molecules for Efficient Magnesium Metal Anodes

ABSTRACT Rechargeable magnesium batteries offer a compelling pathway toward sustainable energy storage, yet realizing this vision demands scalable electrolytes formulated with widely accessible salts, such as magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI) 2 ). Progress in Mg(TFSI) 2 ‐based electrolytes has been severely hindered by low Mg stripping/plating efficiency, arising from sluggish Mg 2+ desolvation kinetics and uncontrolled interfacial reactions. Herein, we adopt a descriptor‐informed molecular screening approach and identify 4‐bromo‐N, N‐dimethylaniline (BrNNA) as an interface‐active electrolyte component that enables fast Mg stripping/plating kinetics in Mg(TFSI) 2 ‐based electrolytes. Recognizing their relevance to interface modulation, dipole moment, lowest unoccupied molecular orbital energy, and donor number are employed as quantifiable molecular descriptors to screen a series of substituted aniline derivatives, from which BrNNA emerges as the optimal candidate. The optimized BrNNA‐containing electrolyte supports immediate and stable Mg electrochemistry without activation, sustaining over 2400 h at 0.1 mA cm −2 in symmetric cells and achieving cumulative areal capacities up to 5 Ah cm −2 at 10 mA cm −2 . We reveal that BrNNA participates in Mg 2+ solvation while preferentially adsorbing onto the Mg surface, lowering the Mg 2+ desolvation barrier and directing the formation of a thin Br‐containing interface that facilitates interfacial Mg 2+ transport. Moreover, the electrolyte has been validated in full Mg cells using various cathode materials.