Engineering Compact Solvation Structure of Nonflammable Electrolyte via an Asymmetric Fluorinated Ether to Enable Stable High‐Voltage Lithium‐Ion Batteries With Micron‐Sized Silicon Anodes

ABSTRACT Micron‐sized silicon (µSi) is a promising anode for lithium‐ion batteries due to its abundant resource, high theoretical capacity, and low cost. However, their substantial volume changes during the charge/discharge process necessitate a robust solid electrolyte interphase (SEI) with enhanced mechanical stability. Herein, we engineer a compact solvation structure through the introduction of a novel flame‐retarding asymmetrically fluorinated ether (AHEE), thereby facilitating preferential anion decomposition to construct a robust SEI of µSi in carbonate‐based electrolytes. Molecular dynamics simulations and Raman spectra reveal closer Li + ‐anion distances and an increased aggregate proportion, respectively. This originates from the molecular design of AHEE, where steric hindrance and electron‐withdrawing effects of the fluorinated segment promote an anion‐rich solvation structure, while the ethoxy terminus maintains moderate Li + coordination, collectively promoting a compact solvation structure and facilitating maximized anion participation to form an inorganic‐rich SEI. Ultimately, stable high‐voltage cycling of µSi‐based full cells is achieved for enhanced electrolyte oxidation resistance and robust SEI, suppressing the volume expansion of µSi anodes. Consequently, µSi||LiNi 0.8 Co 0.1 Mn 0.1 O 2 full cells deliver a capacity retention of 78.3% under a high voltage of 4.6 V, and µSi||LiFePO 4 cells achieve a high capacity retention of 98.2% after 200 cycles. This solvation engineering strategy presents a promising avenue for developing next‐generation high‐voltage batteries with silicon‐based anodes.