In Situ Growth of Covalent Organic Frameworks on Carbon Nanotubes for High‐Performance Potassium‐Ion Batteries

Redox‐active covalent organic frameworks (COFs) have been demonstrated as promising organic electrodes in many electrochemical devices. However, their inherently low conductivity significantly hinders the full utilization of their internal redox‐active sites. To address this issue, a simple solvothermal method is used to in situ polymerize 2,4,6‐triformylphloroglucinol (TP) and p‐phenylenediamine (PA) on the surface of carbon nanotubes (CNTs), generating a nanocable‐like COF‐based nanocomposite, TpPa‐COF@CNT nanocables, which contain abundant β‐ketoenamine groups. By combining the high specific surface area and dense active sites of COFs with the superior conductivity of CNTs, the TpPa‐COF@CNT nanocables as the anode in potassium‐ion batteries displayed excellent performance. The reason is that the isomerization between the enolic and keto forms reinforces the stability of molecular architecture, while the transformation of active sites from C=N to C=O improves the K+ adsorption capability. Notably, the TpPa‐COF@CNT nanocable anode exhibits a high reversible capacity of 446.1 mAh g−1 at 0.1 A g−1 and maintains 282.5 mAh g−1 even after 2000 cycles at a higher current density of 2.0 A g−1. Additionally, a full battery assembled with 3,4,9,10‐Perylenetetracarboxylic dianhydride heat‐treated at 450 °C as the cathode retains a reversible capacity of 273.6 mAh g−1 after 200 cycles at 0.1 A g−1.