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

ABSTRACT 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 N 3 ‐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 = PF 6 − , ClO 4 − , BF 4 − , 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.