Rational Design of Cu₃Si Interphase for 3D Micron‐Sized SiOC‐based Anode to Enable Long‐Term Cycling of Lithium‐Ion Battery

Abstract The low effective capacity, inferior initial Coulombic efficiency, and unstable solid electrolyte interface (SEI) of silicon oxycarbide (SiOC) materials in lithium‐ion batteries (LIBs) pose significant challenges for the widespread application. Herein, to circumvent these issues, a micron‐sized SiOC‐based anode with 3D structure is constructed by Si and Cu co‐doping using solvent‐free ball milling for high‐performance LIBs. The Cu₃Si alloy is formed in situ as an intermediate that is anchored to the surface of Si within the SiOC matrix. The unique 3D SiOC‐based anode with Cu₃Si interphase provides fast electron conductivity and high mechanical strength, while facilitating the formation of a robust and LiF‐rich SEI. Specifically, the SiOC‐based anode delivers excellent cyclic stability and rate capability (750.0 mAh g⁻¹ for 1000 cycles at 1 A g⁻¹). Notably, the full cells equipped with an NCM811 cathode maintain this cyclic stability, achieving a 93.0% capacity retention after 150 cycles. This work provides insights into the rational fabrication of a 3D micron‐sized SiOC‐based anode with an in situ generated Cu₃Si interphase for advanced LIBs and beyond.