Molecular Engineering of Dual-Ion Regulated Covalent Organic Frameworks for Dendrite Suppression in Solid-State...

Poly(ethylene oxide) (PEO) solid electrolytes offer processability, flexibility and low-cost, yet their poor ionic conductivity and limited dendrite suppression capability impedes practical applications. Despite advances in Li⁺ transport kinetics, performance degradation persists due to space-charge polarization induced by uncontrolled anion migration. Here, we present a covalent organic framework (COF) for synchronous cation and anion regulation. By integrating lithiophilic methoxy groups and anionophilic imidazolium species into a single framework, this ionic COF (ICOF) enables synergistic ion management in PEO electrolytes. Ordered channels with fast-hopping sites facilitate rapid Li⁺ conduction, while cationic sites immobilize TFSI^- anions, preventing anion depletion and subsequent space-charge polarization. This dual-ion regulation leads to an Li⁺ transference number of ∼0.72 and effective dendrite mitigation in symmetric-cells as well as full-cells with LiFePO₄ and high-voltage NCM811 cathodes. By engineering COFs with spatially segregated yet functionally complementary motifs, selective anion immobilization alongside fast cation transport is achievable, potentially breaking the conventional trade-offs that have limited PEO-based lithium metal batteries.