Covalent Organic Frameworks as Promising Electrode Materials for High-Valent Ion Rechargeable Batteries

Covalent organic frameworks (COFs), porous topological crystalline polymers whose molecular structure can be flexibly adjusted to accommodate a variety of metal ions with different radii and effectively buffer the volume expansion of electrodes, have become a promising electrode material for high-valent metal-ion batteries (HMIBs). This Forum Article reviews the research history and recent progress of COF electrode materials in the fields of zinc-ion batteries, magnesium-ion batteries, calcium-ion batteries, and aluminum-ion batteries. By discussing the material design and charge storage mechanism, the existing problems of current HMIB materials, such as low conductivity and low specific capacity due to high molecular weight, are summarized. Finally, strategies to improve the performance of HMIBs are suggested from the perspectives of active centers, electronic conductivity, electrolytes, characterization techniques, and theoretical exploration of electrode materials.