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

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.