A LiF/Sn–Li Hybrid SEI Layer Constructed via Chemical Prelithiation To Enhance Mechanical Robustness and Li + Transport Kinetics of SiO Anodes for High-Energy Lithium-Ion Batteries

Silicon monoxide (SiO), with its high specific capacity and low discharge voltage plateau, stands out as a promising anode material for high-energy lithium-ion batteries. However, the application of SiO anodes suffers from an inferior initial Coulombic efficiency (ICE), the instability of the solid electrolyte interface (SEI) layer, and inferior Li⁺ transport kinetics, leading to unsatisfactory cycling stability and rate capability. Herein, a LiF/Sn-Li hybrid SEI layer is in situ constructed on chemically prelithiated SiO by spontaneous reaction with SnF₂ (SnF₂-SiO), driven by the redox potential difference between SnF₂ and Li, which induces the reductive decomposition of SnF₂ and interfacial chemical transformation. Chemical prelithiation compensates for irreversible lithium loss by introducing additional active lithium, thereby enhancing the ICE of the SiO anodes. Notably, the cooperative effect of LiF and Sn-Li alloy stabilizes the electrochemical interface, enhances Li⁺ diffusion kinetics, and reduces charge transfer resistance. As expected, the SnF₂-SiO delivers a remarkable ICE (99.7%) and cycling stability (1126.0 mAh g^-1 after 200 cycles), together with superior overall performance for lithium-ion full batteries (SnF₂-SiO//LiFePO₄). This work confirms the significance of chemical prelithiation and regulation of the hybrid SEI layer for advancing silicon-based anodes in high-performance lithium batteries.