Thiophene‐Based Bipolar‐Type Covalent Organic Frameworks with Extended π‐Conjugation as Superior Cathode for Lithium‐Ion Batteries

Abstract Covalent organic frameworks (COFs) have latterly emerged as a promising platform for devising electrode materials used to acquire high‐performance lithium‐ion batteries (LIBs). However, the preparation of COFs with fast redox kinetics, high‐efficiency utilization of active sites, superior stability, and high conductivity remains a challenge. Herein, a thiophene‐based bipolar‐type COFs (denoted as TT‐TPDA‐COF) featuring extended conjugation, rich multiple redox‐active sites (C─S, C─N, and C═N), and hierarchical micro‐mesoporosity is synthesized. TT‐TPDA‐COF exhibits significantly increased density of redox‐active sites and enhanced electrical conductivity compared with its corresponding counterpart (Np‐TPDA‐COF). Remarkably, when TT‐TPDA‐COF is used as LIBs cathode, it shows exceptional specific capacity up to 309 mA h g−1 at 200 mA g−1, significantly surpassing that of Np‐TPDA‐COF (195 mA h g−1 at 200 mA g−1), high energy density of 714 W h kg−1, superb rate property (182 mA h g−1 at 5000 mA g−1), and impressive capacity preservation of 84.3% after 5000 cycles at 5000 mA g−1. Additionally, the predictable application of TT‐TPDA‐COF for prototype batteries has been proved by the high‐performance dual‐ion full cells assembled by using TT‐TPDA‐COF as cathode. Furthermore, the dual‐ion storage mechanism of TT‐TPDA‐COF is comprehensively revealed by in/‐ex situ studies and theoretical calculations.