Covalent-Organic-Framework Enabled Efficient Three-dimensional K-storage via Electrolyte Solvation Manipulation.

Covalent-organic-framework (COF) materials with a designable periodic framework have been expected as a kind of promising anode material for potassium ion batteries (PIBs). However, these materials suffer seriously from low capacity, poor rate performance, and slow reaction kinetics during the K-storage process, significantly limiting their widespread applications. Herein, a three-dimensional (3D) COF material denoted as CN-COF with a high N content and defined configuration as well as a graphite-like layer stacking structure was developed as a promising anode to realize efficient 3D K-storage performance with enhanced interfacial stability and reaction kinetics via an electrolyte chemistry compatibility strategy. Particularly, a uniform and stable solid-electrolyte interphase (SEI) with rich inorganic components was controllably formed in the optimized high-concentration THF-based electrolyte (HTE), ensuring satisfactory cycling stability as well as rapid diffusion kinetics. As a result, the synthesized CN-COF material in this optimized electrolyte delivered a high reversible capacity of 385.8 mAh/g at 50 mA/g, and a well-maintained 95.3 mAh/g after 1500 cycles at 500 mA/g. This work provides innovative design and manipulation of the K-storage mechanism via the synergistic effect between nanostructure design and electrolyte chemistry for advanced K-storage materials.