Poly(ethylene glycol)-functionalized 3D covalent organic frameworks as solid-state polyelectrolytes

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Existing 2D covalent organic frameworks (COFs) for lithium-ion conduction face challenges with uniform channel stacking and ion transport at interfaces.
• Powdered COFs exhibit limited ion mobility due to grain boundary and contact resistance issues.

Purpose of the Study:

• To develop novel three-dimensional (3D) COFs with improved ion transport properties for lithium-ion conduction.
• To enhance the performance and safety of lithium-ion batteries by addressing limitations in current solid-state electrolytes.

Main Methods:

• Synthesis of poly(ethylene glycol) (PEG)-functionalized 3D COFs with interconnected channels.
• Incorporation of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) into the 3D COF structure.
• Measurement of ionic conductivity at elevated temperatures.

Main Results:

• Successfully constructed 3D COFs with multi-directional ion conduction pathways.
• Achieved a high ionic conductivity of 3.6 × 10^-4 S cm^-1 at 260 °C with PEG-functionalized 3D COFs and LiTFSI.
• Demonstrated superior thermal stability compared to commercial organic electrolytes.

Conclusions:

• PEG-functionalized 3D COFs effectively reduce interfacial resistance and facilitate ion transport.
• These materials show significant promise as safe, high-temperature solid electrolytes for advanced lithium-ion batteries.