Carbonyl Engineering in Covalent Organic Frameworks for Promoting Li ⁺ Conduction

ABSTRACT

The rational design of covalent organic frameworks (COFs) for solid‐state electrolytes (SSEs) is hindered by the precise position of polar functional groups (C ═ O) affect Li ⁺ transport. Herein, we synthesize four COFs materials with systematically carbonyl substitution positions to elucidate their structure–property relationships. Among them, the β‐ketoenamine‐based COF featuring ortho‐dicarbonyl groups exhibits a significantly enhanced electronegativity, which restricts anion migration and promotes selective Li ⁺ transport. Consequently, the rich‐carbonly COF SSE achieves a high ionic conductivity of 9.83 × 10 ⁻⁴ S/cm, a Li ⁺ transference number of 0.8, and an electrochemical stability window exceeding 5.1 V. Symmetric cell delivers stable Li plating/stripping for over 1200 h at 0.2 mA/cm ² with a low overpotential of ∼0.1 V, and over 460 h at 0.5 mA/cm ² . When coupled with a LiFePO ₄ cathode, the solid‐state battery retains 80% capacity after 1230 cycles at 1 C and 80.2% after 700 cycles at 5 C. Theoretical calculations reveal that the ortho‐dicarbonyl coordination environment lowers the Li ⁺ migration barrier (0.376 eV) and enhances Li ⁺ –framework affinity, accelerating charge transfer. This work establishes a clear correlation from functional group positioning to pore chemistry, ion transport kinetics, and interfacial stability, offering a molecular‐level design principle for high‐performance COF‐based solid‐state electrolytes.