Lithium Carbide Prelithiation Agent‐Coated Separator Facilitates Compact Expansion of Silicon Electrode

Abstract The high specific capacity and safety nature of silicon (Si) anode has garnered significant attention and investment for its application in high‐energy‐density lithium‐ion batteries (LIBs). However, the Si anode exhibits low initial Coulombic Efficiency (CE) and compromised cycle stability due to interfacial side reactions and the volume expansion of Si particles. Here, a straightforward strategy is proposed to prelithiate Si anodes and enhance the cycle stability by utilizing a lithium carbide (LiC ₆ ) coated separator. By incorporating a LiC ₆ prelithiation agent‐coated PP/PE separator (PP/PE@LiC ₆ ), a robust interaction between PP/PE@LiC ₆ and Si anode forms during cycling, which significantly reduces subsequent contact between the electrolyte and Si particles, thereby minimizing excessive electrolyte decomposition during cycling, and facilitates the compact expansion of the Si electrode. In Si|PP/PE@LiC ₆ |Li cell, the initial CE reaches 108.51%, showcasing enhanced electrochemical stability (77.93% after 100 cycles). Moreover, the Si|PP/PE@LiC ₆ |LiFePO ₄ cell also exhibits exceptional initial CE of ≈93.02% and improved electrochemical stability (100.94% after 100 cycles at 0.33C). This study introduces a secure and readily attainable prelithiation method for industrial applications of high‐energy density Si‐based batteries.