p/n-Type Polyimide Covalent Organic Frameworks for High-Performance Cathodes in Sodium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Organic Chemistry

Background:

• Covalent organic frameworks (COFs) offer tunable structures for advanced battery applications.
• Developing efficient organic electrode materials is crucial for next-generation energy storage.

Purpose of the Study:

• To synthesize and characterize novel COFs for sodium-ion battery (SIB) cathodes.
• To enhance the electrochemical performance of COFs through structural modification and composite formation.

Main Methods:

• Synthesis of p-type TPDA-TA-COF and subsequent postsynthetic modification to create n-type TPDA-NDI-COF.
• Incorporation of carbon nanotubes (CNTs) into the TPDA-NDI-COF matrix.
• Electrochemical testing of COF-based electrodes in SIBs.

Main Results:

• TPDA-NDI-COF exhibits dual redox-active centers and a wide potential window (1.0–3.6 V vs Na+/Na).
• TPDA-NDI-COF delivered double the capacity (67 mAh g−1) of TPDA-TA-COF (28 mAh g−1).
• TPDA-NDI-50%CNT composite achieved 120 mAh g−1 at 0.02 A g−1 and retained 92 mAh g−1 after 10,000 cycles at 1.0 A g−1, with an average discharge voltage of 2.1 V.

Conclusions:

• The tailored TPDA-NDI-COF, especially when composited with CNTs, demonstrates superior performance as a cathode material for SIBs.
• The developed COF materials show potential for high-performance and stable sodium-ion energy storage.
• This work highlights the effectiveness of postsynthetic modification and composite strategies for optimizing COF-based electrodes.