Programming ionic covalent organic framework solid-state electrolytes for rechargeable batteries: From 2D to 3D

Covalent organic frameworks (COFs) are revolutionizing the solid-state ionics by programming backbone, incorporating functional groups, and chelating with specific ions in structural units to facilitate rapid ion transport. More encouragingly, topology diagrams enable COFs with tremendous possibilities in structural design from two-dimensional (2D) to three-dimensional (3D) polygonal network, thus positioning themselves as promising ionic solid-state electrolytes for energy storage and conversion. This review summarizes recent advances in COF electrolytes from 2D to 3D, focusing on how pore topology, framework functionality, and composite designs regulate Li⁺ conduction. Mechanistic insights including anion immobilization, backbone–ion interactions, and solvent- or polymer-assisted transport are discussed to elucidate the structure–transport correlations that govern ionic conductivity and interfacial behavior. Key limitations, such as modest intrinsic conductivity, electrode interfacial resistance, and mechanical fragility, are critically examined. Beyond lithium systems, the broader potential of COFs as versatile solid-state ionic conductors for emerging metal-ion batteries is highlighted. Finally, future opportunities are outlined, including ionic-backbone engineering, nanochannel ordering, quasi-solid architectures, dendrite-regulating interfaces, and scalable membrane processing. We earnestly expect that this review will further elucidate pathways for the advancement of COF-based electrolytes toward practical and high-performance solid-state rechargeable batteries.