Self-Standing Covalent Organic Polymer Membrane with High Stability and Enhanced Ion-Sieving Effect for Flow Battery

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Ion-conducting membranes are vital for safe renewable energy integration via flow batteries.
• Covalent organic polymer (COP) membranes offer rapid and selective ion transport but face challenges in scalability, mechanical robustness, and chemical stability.

Purpose of the Study:

• To develop a mechanically robust, chemically stable, and scalable self-standing covalent organic polymer (COP) membrane with precisely controlled sub-nanometer pores for flow battery applications.

Main Methods:

• In situ polymerization utilizing irreversible secondary amine linkages to create COP membranes.
• Characterization of membrane pore size (4.5–6.4 Å) and ion selectivity (proton and vanadium ions).
• Electrochemical testing of the membrane in an all-vanadium redox flow battery (VFB) over 1000 cycles.

Main Results:

• Fabrication of a self-standing COP membrane with continuous sub-nanometer channels via a simple and efficient in situ polymerization approach.
• Demonstrated enhanced selectivity for proton and vanadium ions, alongside excellent electrochemical stability.
• Achieved over 80% energy efficiency at 200 mA cm⁻² current density over 1000 cycles in an all-vanadium redox flow battery.

Conclusions:

• The developed COP membrane offers a promising solution for advanced ion-sieving applications in flow batteries.
• This work provides valuable insights into designing COP-based membranes for sustainable energy storage.
• The membrane's performance highlights its potential for improving the efficiency and safety of grid-scale renewable energy storage systems.