Durable Interphase Engineering on SiO x Anodes Through Interfacial‐Enrichment‐Facilitated Polymerization

ABSTRACT Constructing a robust solid electrolyte interphase (SEI) is a proven strategy to enhance the performance of Si‐based anodes by accommodating severe volume swings and suppressing interfacial side reactions. However, existing strategies that rely solely on either chemical coating or electrochemical formation struggle to reconcile SEI uniformity and long‐term stability. Here, we propose a synergistic strategy that integrates the interfacial modification with in situ regulated electrolyte decomposition. A conformal layer composed of LiF and Li 3 PO 4 is pre‐formed on SiO x anodes, where LiF serves as a stable mechanical framework for the inorganic‐rich SEI, and Li 3 PO 4 selectively adsorbs fluoroethylene carbonate (FEC), favoring the polymerization of FEC‐derived species via interfacial enrichment to form the high‐molecular‐weight organic species. These electrochemically generated SEI components effectively compensate for the damage to the initial coating caused by volume expansion, enabling the SEI to possess both structural integrity and resilience. Consequently, the modified SiO x anode exhibits benchmark electrochemical performance, delivering excellent cycling stability (1086 mA h g −1 , 81% capacity retention for 300 cycles at 0.8 A g −1 ) and high‐rate capability (1010 mAh g −1 at 2.4 A g −1 ). This work establishes a precedent for the dynamic repair interphase design paradigm for high‐capacity anodes.