A Highly Crystalline Covalent Organic Framework with Rich Redox Active Sites as Cathode Material for Lithium Batteries

Covalent organic frameworks (COFs) have been regarded as promising cathode materials for lithium batteries. However, they generally show low practical capacity. Here we report the design, preparation, and battery application of a highly crystalline two‐dimensional truxenone‐based COF (TRO‐BT‐COF) with rich redox active sites, realizing a high practical capacity. In‐situ characterizations and theoretical calculations indicate that the lithiation reaction proceeds successively on C=O and C=N groups of TRO‐BT‐COF. One ring of TRO‐BT‐COF can theoretically store 27 Li+ ions through two stages. Consequently, the highly crystalline TRO‐BT‐COF displays a high discharge capacity of 435 mAh g–1 when used as cathode material for lithium batteries. This work provides a facile approach to achieve COF electrode materials with high practical capacity for lithium batteries.