Interface‐Anchored Cu‐COF Frameworks Mitigate Volume Expansion and Accelerate Li + Transport in Silicon Anodes

ABSTRACT Silicon anodes, despite their exceptionally high theoretical capacity, suffer from drastic volume fluctuations and sluggish charge transfer kinetics upon cycling, resulting in rapid capacity degradation and suboptimal rate capability. Herein, we report a novel interface‐anchored copper covalent organic framework that simultaneously mitigates mechanical degradation and accelerates lithium‐ion transport within silicon anodes. The Cu‐COF coating, constructed via the C ═ N bond formed through the Schiff base reaction between amino and aldehyde groups and Cu 2+ coordination with N/CH 3 COO − forms a robust and porous interfacial framework uniformly encapsulating silicon nanoparticles. Such a structure acts as a stress‐buffering shell to accommodate volume expansion, reducing electrode swelling from 373% to 201%, and establishes efficient lithium‐ion transport channels through the Cu‐centered coordination network. Consequently, the optimized Si@6% Cu‐COF electrode exhibits a rechargeable capacity of 1010.6 mAh g −1 after 500 cycles at 1 A g −1 , while maintaining 1083.4 mAh g −1 even at 5 A g −1 , outperforming Silicon electrodes by a wide margin. More significantly, the benign coordination and electrochemical stability of acetate ions render the Cu(OAc) 2 ‐derived Cu‐COF intrinsically more durable and chemically stable than derived by CuCl 2 , Cu(NO 3 ) 2 and CuSO 4 . This study provides novel insights into the rational design of silicon‐based lithium‐ion batteries of high energy density.