Multiple Redox‐Active Centers in An Azatriangulenetrione‐Based Covalent Organic Framework for High‐Capacity, High‐Rate and Ultra‐Stable Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) suffer from sluggish kinetics, large volume change, and limited specific capacity due to the large radius of Na+. These issues can be solved through using covalent organic frameworks (COFs) as electrodes. Herein, an azatriangulenetrione‐containing COF (denoted as CityU‐33) was designed and synthesized as an electrode material for SIBs. Due to its inherent abundance of multiple redox‐active sites and fast intercalation kinetics, CityU‐33 delivered a high discharge capacity of 410.4 mAh g‐1 at 0.1 A g‐1 and showed remarkable long‐term cycling stability, where a discharge capacity of 313 mAh g‐1 at 0.2 A g‐1 with approximately 100% retention over 1700 cycles was achieved, making it the top COF electrode material for SIBs.