Molecular and Structural Engineering of Single Li⁺ Ion Conducting Covalent Organic Framework Electrolytes for High-Performance Solid-State Lithium-Metal Batteries

Covalent organic frameworks (COFs) are promising solid-state electrolytes (SSEs) for lithium-metal batteries. Their structural tunability, ordered nanochannels, and suppressed segmental motion facilitate Li⁺ ion transport at ambient temperatures. Nevertheless, the ionic conductivity of most COF-based SSEs are limited by suboptimal Li⁺ conduction pathways and structural deficiencies such as poor crystallinity and grain boundary formation. Here, we report a combined computational and experimental design of disulfonate-functionalized COF film with a thickness of 20 µm, exhibiting an ionic conductivity of 1.01 × 10^‒4 S cm^‒1 at 25 °C. At the molecular level, the incorporation of immobile disulfonate anions and carbonyl groups complementarily allows for inter-sub-channel Li⁺ ion hopping with minimal spatial separation. Extensive molecular dynamics (MD) simulations accounting for the field-applied conduction process highlight an optimized Li⁺ ion transport pathway enabled by our molecular design of the COF structure. Structurally, the COF films were synthesized via a solution-phase processing method, yielding thin, uniform layers with improved crystallinity, reduced grain boundaries, and smooth surface morphology. These structural improvements directly translated into superior electrochemical performance, demonstrating the importance of integrated molecular and structural engineering in designing high-performance COF electrolytes.