Engineering 4‐Connecting 3D Covalent Organic Frameworks with Oriented Li+ Channels for High‐Performance Solid‐State Electrolyte in Lithium Metal Battery

Abstract The development of rapid and stable ion‐conductive channels is pivotal for solid‐state electrolytes (SSEs) in achieving high‐performance lithium metal batteries (LMBs). Covalent organic frameworks (COFs) have emerged as promising Li‐ion conductors due to their well‐defined channel architecture, facile chemical tunability, and mechanical robustness. However, the limited active sites and restricted segmental motion for Li+ migration significantly impede their ionic conductivity. Herein, a rational design strategy is presented to construct 3D porous COF frameworks (TP‐COF and TB‐COF) using linear ditopic monomers connected via C─C and C─N linkages. These COFs, integrated with polymer electrolytes, provide enhanced Li+ transport pathways and stabilize lithium anodes in LMBs. The TB‐COF, featuring larger pore apertures and abundant ─C═N─ active sites, facilitates superior Li+ conduction (8.89 × 10−4 S cm−1) and a high transference number (0.80) by enhancing lithium salt dissolution. LiF/Li3N‐rich SEI enables uniform Li deposition, enabling PEO‐TB‐COF SSEs to achieve >1000 h stability at 1 mA cm⁻2 while retaining 90% capacity through 800 cycles (0.5 C) in LFP||Li cells. Molecular dynamics simulations and COMSOL Multiphysics modeling reveal that extended Li+ transport channels and reduced interfacial diffusion barriers are key to enhanced performance.