Robust Fully Aromatic‐Conjugated Covalent Organic Frameworks for High‐ Performance and Wide‐Temperature‐Range Cathodic Potassium‐Ion Storage

Abstract Synthesizing covalent organic frameworks (COFs) with robustness and temperature adaptability for advanced potassium‐ion battery (PIB) cathodes remains challenging. Here, robust, fully aromatic‐conjugated COFs with abundant redox‐active sites are reported, synthesized through condensation of 2,3,7,8‐tetraaminophenazine‐1,4,6,9‐tetraone and hexaketocyclohexane octahydrate (HATN‐TAPT COF). The porous and flexible architecture accommodates volumetric changes during potassiation/depotassiation processes. Additionally, optimized flame‐retardant electrolytes enhance PIB safety. As a cathode, it demonstrates an unprecedented capacity of 455 mAh g −1 at 0.1 A g −1 , with a median voltage of 1.89 V, yielding an energy density of 860 Wh kg −1 cathode . The material also exhibits excellent rate capacity (209 mAh g −1 at 10.0 A g −1 ), delivering an exceptional power density of 18 900 W kg −1 cathode . The aromatic‐conjugated structure provides superb structural stability, with remarkable cycling performance of 235 mAh g −1 at 1.0 A g −1 after 5000 cycles and a low decay rate of 0.0045% per cycle, superior to the best‐reported organic PIB cathodes. More importantly, the K//HATN‐TAPT COF cell exhibits all‐weather working potential, demonstrating wide‐temperature adaptability from −30 °C (355 mAh g −1 at 0.02 A g −1 ) to 60 °C (387 mAh g −1 at 0.5 A g −1 ), making it highly promising for extreme environments such as space, high‐altitude regions, and tropical zones.