A co-derived fluorinated SEI via chemical prelithiation toward stable and high-energy silicon-based lithium-ion batteries

Silicon is a promising anode material for next-generation lithium-ion batteries (LIBs) due to its high specific capacity and low cost. However, its practical application is severely hindered by significant volume expansion during lithiation and delithiation, which causes mechanical stress and instability of the solid electrolyte interphase (SEI). These issues lead to poor cycling performance and low initial Coulombic efficiency (ICE), posing substantial challenges for commercial implementation. Herein, we propose an innovative strategy of co-derived fluorinated SEI pre-construction through chemical prelithiation, employing a 2-fluorobiphenyl-lithium-dimethyltetrahydrofuran (2-F-BP-Li-2MT) system designed for silicon-carbon (Si@C) anodes. Unlike conventional prelithiation methods that solely compensate for lithium loss, simultaneously forming a robust SEI layer enriched with lithium fluoride (LiF) components directly on the surface of Si@C. The co-derived fluorinated SEI exhibits a unique “fluorine-homogeneous” structure during cycling, significantly enhancing mechanical durability and facilitating rapid Li + transport. The chemically prelithiated Si@C anodes with co-derived fluorinated SEI (Pr-F-Si@C) achieve a high ICE of 99.5 % and remarkable capacity retention of 86.3 % after 300 cycles. Furthermore, the assembled full cells (LiFePO 4 //Pr-F-Si@C) deliver high energy density (246.3 Wh kg −1 , based on total mass) and stable cycling performance. This work provides critical insights into interface design and prelithiation, providing new pathways toward practical high-energy and long-life Si-based batteries.