Molecular Engineering of Dual–Ion Regulated Covalent Organic Frameworks for Dendrite Suppression in Solid–State Lithium Metal Batteries

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.