Two-dimensional fused π-conjugated multi-activity covalent organic framework as high-performance cathode for lithium-ion batteries

Abstract

Electrochemically active covalent organic frameworks (COFs) with robust skeletons and permanent porosity are attracting wide interest as promising electrode materials for Li-ion batteries (LIBs). However, current COF-based electrodes suffer from poor capacity and rate performance due to limited redox-active sites and low conductivity. To address these challenges, combining the advantages of high stability of the macromolecular skeleton and high-density redox-active C--O and C--N groups, a novel two-dimensional (2D) fused pi-conjugated COF (denoted as HAPT-COF) with ultrahigh theoretical capacity is fabricated. In particular, the post-hydrothermal reaction between HAPT-COF and graphene oxide (GO) affords intercalated COF-based nanocomposites (HAPTCOF@rGO), featuring with improved utilization of redox-active sites, electronic conductivity, and structure stability. The C--O and C--N groups on the walls contribute to reversible 18 Li-ions storage for each HAPT-COF repeating unit across three stages. Owing to these advantages, the HAPT-COF@rGO exhibited an excellent reversible capacity (558 mAh g- 1 at 0.1 C), cycling stability (92% capacity retention after 1000 cycles at 10 C), and superior rate performance (318 mAh g- 1 at 10 C), ranking the best among reported polymer cathodes in LIBs.