The application of Si-based anodes in lithium-ion batteries (LIBs) has garnered significant attention due to their high theoretical specific capacity yet is still challenged by the substantial volume expansion of silicon particles during the lithiation process, resulting in the instability of the electrode-electrolyte interphase and deteriorative battery performance. Herein, an ortho(trimethylsilyl)oxybenzene electrolyte additive, 1,2-bis((trimethylsilyl)oxy) benzene (referred to as BTMSB), has been investigated as a bifunctional electrolyte additive for Si-based LIBs. The BTMSB can form a uniform and robust LiF-rich solid electrolyte interphase (SEI) on the surface of Si-based material particles, adapting the huge volume expansion of the Si-based electrode and facilitating lithium-ion transport. Additionally, the BTMSB demonstrates the ability to scavenge hydrofluoric acid (HF) to stabilize the electrode-electrolyte interphase. The SiO x /C∥Li batteries with 2% BTMSB exhibit improved cycle performance and current-rate capabilities, of which the capacity retention retains 69% after 400 cycles. Furthermore, Si-based anode cells with higher theoretical specific capacities (1C = 550 mAh g -1 ) and NCM523∥SiO x /C pouch cells are constructed and evaluated, displaying superior cycle performance. This work provides valuable insights for the development of effective electrolyte additives and the commercialization of high energy density LIBs with Si-based anodes.