Being considered as a promising anode material for next‐generation lithium‐ion batteries, silicon oxide (SiOx) suffers from low initial coulombic efficiency and unstable solid–electrolyte interphase (SEI), which hinder its commercial use. To address these issues, herein, an optimized chemical prelithiation method is developed using a molecularly engineered lithium–biphenyl‐type complex, which facilitates improved prelithiation efficiency. More importantly, owing to the reaction between the prelithiation agent and sodium carboxymethyl cellulose binder, a stable artificial SEI layer with hard inorganic particles embedded in soft organic matrix can be preformed on the surface of the SiOx anode after prelithiation. The preformed SEI layer remains stable during long‐term cycling, contributing to significant improvement of capacity retention (87.4%) over pristine SiOx (68.6%) after 100 cycles at 0.2 C. Through demonstrating a hitherto unknown interfacial constructing strategy for SiOx, this study provides a fresh perspective on realizing high‐capacity Si‐based anodes. Herein, more efficient chemical prelithiation in SiOx anode is achieved via molecular engineering. Through the reaction with sodium carboxymethyl cellulose binder, a robust solid–electrolyte interphase (SEI) with higher contents of LiF and Li2CO3 can be obtained during prelithiation, resulting in significant improvement in both initial coulombic efficiency and cycling stability of SiOx anodes.