Covalently Anchored, LiF‐Reinforced Rigid‐Flexible Interphase for Stable Nano‐Si Anodes

Silicon‐based materials are ideal alternatives to conventional graphite anodes in lithium‐ion batteries due to their exceptionally high theoretical capacity. However, the dramatic volume changes of silicon during lithiation/delithiation cause pulverization of active particles and repeated fracture and reformation of the solid electrolyte interphase (SEI) film, severely hindering practical applications. Here, a covalent anchoring in situ crystallization (CAIC) strategy is proposed to construct a multifunctional modification layer composed of triglyme (G3) and nano‐sized LiF on the nano‐silicon surface (denoted as nSi@G3‐LiF). This unique architecture provides multiple synergistic effects: high‐modulus LiF and flexible ether‐chain network buffer volume expansion and dissipate mechanical stress; abundant oxygen coordination sites enable rapid Li + transport; and LiF nanocrystals induce a dense, inorganic‐rich SEI layer that effectively suppresses parasitic reactions. Consequently, the nSi@G3‐LiF electrode achieves a remarkably high initial Coulombic efficiency of 91.3%, outstanding rate capability (1754, 1631, and 1301 mAh g −1 at 2, 3, and 5 A g −1 , respectively), and superior long‐term cycling stability, retaining 1465 mAh g −1 after 900 cycles at 2 A g −1 . This work presents an effective strategy for regulating interfacial mechanics and kinetics through chemical bonding coupled with in situ crystallization reinforcement, offering new insights into interfacial design for silicon‐based anodes.