Recent Progress in Covalent Organic Frameworks for Cathode Materials

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Covalent organic frameworks (COFs) are polymers built from organic molecules linked by reversible covalent bonds.
• COFs offer tunable pore sizes and ordered structures, beneficial for ion transport in energy storage.
• Redox-active COFs are emerging as promising cathode materials, but their energy density requires improvement.

Purpose of the Study:

• To review recent advancements in redox-active COFs for energy storage applications.
• To categorize COFs based on their redox-active functional groups.
• To summarize key properties including structure, synthesis, surface area, specific capacity, and voltage.

Main Methods:

• Literature review of COFs containing redox-active functional groups (-C=O-, -C=N-, -N=N-).
• Classification of COFs into six subcategories based on distinct active functional groups.
• Compilation of data on structural characteristics, synthesis units, specific surface area, specific capacity, and voltage range.

Main Results:

• Identified six distinct subcategories of redox-active COFs based on functional groups.
• Detailed the structure-property relationships influencing performance in cathode applications.
• Highlighted that current COF cathode voltages (2-3 V vs. Li) offer room for enhancement, with research focusing on increasing specific capacity via more active sites.

Conclusions:

• Redox-active COFs present a versatile platform for high-performance energy storage.
• Systematic categorization aids in understanding and designing COFs for specific applications.
• Further research is needed to enhance the voltage output and overall energy density of COF-based cathodes.