Electrolyte-Framework Matching in High-Voltage TEMPO-COF Cathodes for Lithium Batteries

High-voltage organic cathodes based on stable nitroxyl radicals are promising candidates for sustainable energy storage. However, porous TEMPO-based frameworks remain underdeveloped compared to linear polymers, and the role of electrolyte anions in governing their performance is poorly understood. Herein, two imine-linked covalent organic frameworks (COFs) are post-synthetically functionalized with N₃-TEMPO via click chemistry, affording crystalline, porous TEMPO-TB and TEMPO-TP COFs with uniformly distributed redox-active sites. When evaluated as cathodes for Li-organic batteries, both materials exhibit reversible p-type redox activity at ∼3.6-3.7 V vs. Li/Li⁺. A systematic comparison of LiX electrolytes (X = PF₆ ^-, ClO₄ ^-, BF₄ ^-, DFOB^-, and TFSI^-) in carbonate-based media reveals strong anion-dependent electrochemical behavior. Among the electrolytes studied, LiDFOB provides the best balance of capacity, rate capability, and cycling stability, attributed to favorable anion-coupled charge storage, interfacial charge-transfer behavior, and pseudocapacitive contributions. Binder-free buckypaper electrodes enable up to 80 wt.% active material and mass loadings of 40 mg cm^-2, while maintaining ∼1.3 mAh cm^-2. This represents the highest reported mass loading and areal capacity for TEMPO-based cathodes in lithium batteries. These results establish framework-electrolyte matching as a key design principle for high-voltage TEMPO-based cathodes and provide new guidance for the development of radical-functionalized organic battery materials.