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 288 mAh g^-1 at 0.2 A g^-1 with 97 % retention over 2000 cycles was achieved, making it the top COF electrode material for SIBs.