Ionic Covalent Organic Frameworks for Solid-State Polymer Electrolytes: Synthesis, Ion-Transport Regulation, and...

Solid-state polymer electrolytes are considered promising alternatives to conventional liquid electrolytes for improving the safety and energy density of lithium batteries. However, their practical application is still limited by insufficient room-temperature ionic conductivity, low lithium-ion transference number, poor mechanical robustness, and unstable electrode/electrolyte interfaces. Ionic covalent organic frameworks (iCOFs), as charged and crystalline porous polymers, provide a unique platform for regulating ion transport and interfacial behavior through ordered channels, tunable ionic sites, and designable framework structures. In this review, recent progress in iCOF-based solid-state polymer electrolytes is summarized from a charge-structure-function perspective. First, representative synthetic strategies for iCOFs are discussed, including direct synthesis and postmodification, with emphasis on how ionic-site distribution, crystallinity, pore accessibility, and membrane processability influence electrolyte performance. Subsequently, the applications of cationic, anionic, and zwitterionic COFs in solid-state electrolytes are reviewed. Cationic COFs mainly promote lithium-salt dissociation and anion immobilization. Anionic COFs enable quasi-single-ion or single-ion conduction. Zwitterionic COFs provide dual-charge regulation for Li⁺ transport and interfacial stabilization. The structure-performance relationships of representative iCOF-based electrolytes are critically compared in terms of ionic conductivity, lithium-ion transference number, electrolyte architecture, and battery performance. Finally, the remaining challenges and future opportunities are discussed, including the construction of continuous ion-transport pathways, improvement of polymer-COF compatibility, scalable membrane fabrication, standardized electrochemical evaluation, and clarification of intrinsic ion-conduction mechanisms. This review highlights the potential of iCOFs as functional ion-transport frameworks for safer and higher-performance solid-state lithium batteries.