Carbon-Mediated Lithium Hosting for Prelithiation of Silicon-Hard Carbon Anodes Without Direct Silicon Lithiation.

A chemically stable and potentially scalable prelithiation strategy is developed to improve the initial electrochemical utilization of silicon-hard carbon composite anodes under chemically mild conditions. Chemical prelithiation is widely used to compensate for irreversible lithium loss and improve the initial Coulombic efficiency of silicon-based anodes; however, conventional lithium-arene complexes capable of directly lithiating silicon often suffer from poor chemical stability and limited practical applicability. Here, we employ a chemically stable lithium-biphenyl complex in tetrahydrofuran (Li-BP/THF) that is thermodynamically incapable of directly lithiating silicon. Instead, lithium is preferentially accommodated within the surrounding hard carbon (HC) framework, while SEI pre-formation also contributes to compensating initial lithium loss in silicon-based composite anodes. This carbon-mediated lithiation process simultaneously induces the formation of a uniform inorganic-rich solid electrolyte interphase, which stabilizes interfacial reactions during subsequent cycling. Furthermore, the efficiency of the prelithiation process is governed by the structural characteristics of the HC framework, which can be systematically tuned through controlled heat treatment. Overall, this work establishes Li-BP/THF-mediated carbon-assisted chemical prelithiation as a chemically stable strategy for minimizing initial lithium loss while enhancing interfacial stability in silicon-based composite anodes.