Pre-Fluorinated SEI by Catalyzing a Parasitic Reaction Toward Stable Silicon Anodes

Constructing a robust solid electrolyte interphase (SEI) is critical for batteries. Conventional SEI is formed and repaired through cyclic electrochemical processes that consume active lithium from the cathode, leading to Coulombic losses and capacity decay. Here, we demonstrate an electron-decoupled chemical approach that builds a robust pre-fluorinated SEI through the catalytic reaction of parasitic LiPF₆ hydrolysis at the interface between electrolyte and a designed nanoscale Cu/SiO_x catalytic layer (CL) on micro-sized silicon. The formed LiF-rich SEI is further fortified by the electrocatalytic conversion of the preceding HF byproducts. The resulting anode exhibits a 7% improved initial Coulombic efficiency of 89.3%, remarkable stability over 1600 cycles, and superior rate performance (2670 mAh g^-1 at 5 A g^-1). This strategy of catalytic pre-fluorination offers a powerful pathway to stabilize dynamic electrode interfaces.