Ultra‐Stable, High‐Capacity Anodes Based on Redox‐Active COF Nanotubes for Extreme‐Temperature K‐Ion Batteries

ABSTRACT Covalent organic framework (COF) materials with molecule‐level functionality show great promise as anode materials for K‐ion batteries (KIBs). However, their practical application is hindered by limited capacity and poor cycling stability, especially under extreme temperatures. These issues stem from the large ionic size of K + and thermally induced electrochemical degradation. Herein, we present a COF nanotube with a conjugated periodic skeleton and a high density of redox‐active sites that function as a high‐performance anode for KIBs under room and extreme temperatures. This material, synthesized from 1,5‐diamino‐4,8‐dihydroxyanthracene‐9,10‐dione (DDA) and triformylphloroglucinol (TP), incorporates abundant carbonyl (─C═O) and hydroxyl (─OH) groups as redox‐active centers, enabling high‐capacity potassium‐ion storage. The conjugated periodic framework promotes efficient charge (K + /e − ) transport and ensures structural integrity, while the hierarchical porosity and thin nanotube walls facilitate ion diffusion and minimize volume variation. As a result, the anodes achieve rapid and stable K‐ion storage. Even at 60°C, the COF anode delivers exceptional performance, including outstanding cycling stability (84% capacity retention over 4000 cycles), high initial capacity, and remarkable rate capability (238 mAh g −1 at 6.0 A g −1 ). This work provides new insights into the structural design of COF‐based architecture for high‐performance KIB electrodes operable across a wide temperature range.