Electron Modulation of Solvation Structure for Fire‐Retardant and Fast‐Charging Lithium Metal Batteries

ABSTRACT A critical challenge in advancing lithium metal batteries (LMBs) lies in their aggravated risk of thermal runaway under fast‐charging operation. Trimethyl phosphate (TMP)‐based electrolytes have emerged as promising candidates owing to their cost‐effectiveness and intrinsic flame‐retardant properties. However, the strong interaction between Li + and TMP promotes a TMP‐dominated solvation structure, which significantly restricts Li + transport and forms an unstable solid electrolyte interphase, especially under high‐rate operation. Here, fluoroethylene carbonate (FEC) is introduced as an electron‐modulating additive. The electron‐withdrawing fluorine group in FEC redistributes the charge density of the hydrogen atoms in the methyl groups of TMP, thereby weakening Li + coordination within the TMP‐rich solvation clusters. This modulation reconstructs the solvation structure into an anion‐dominated configuration, accelerates Li + transport kinetics, and markedly enhances fast‐charging performance. As a result, Li||LiFePO 4 cells using the optimized electrolyte deliver a capacity retention of 80.5% after 2,960 cycles at 5 C, corresponding to an ultralow decay rate of 0.0066% per cycle. Even at an ultrahigh rate of 10 C, the cells still retain 90% of their initial capacity after 1,200 cycles. Overall, this electron‐modulated anion‐rich solvation strategy significantly enhances Li + transport and superior fast‐charging capability, providing a viable pathway toward safe, high‐performance LMBs.