Synergistically Tailored Polyacrylonitrile-Based Stable Proton Exchange Membrane for High-Performance Vanadium Redox...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Proton exchange membranes (PEMs) are critical for vanadium redox flow battery (VRFB) performance, influencing stability and capacity retention.
• Minimizing vanadium ion crossover while maintaining high proton conductivity is a key challenge in VRFB development.

Purpose of the Study:

• To synthesize and characterize a novel crosslinked PEM for enhanced VRFB performance.
• To evaluate the membrane's ability to suppress vanadium crossover and improve electrochemical efficiency and long-term stability.

Main Methods:

• Free radical random copolymerization of acrylonitrile, 4-styrenesulfonic acid, and 2-acrylamido-2-methyl-1-propanesulfonic acid.
• Crosslinking the terpolymer using hydrazine hydrate to form the CPAN-PEM-x membranes.
• Characterization of membrane properties including ion-exchange capacity, ionic conductivity, vanadium crossover, and ionic selectivity.
• Testing VRFB performance using the CPAN-PEM-2.5 membrane, assessing coulombic efficiency, voltage efficiency, energy efficiency, capacity retention, and power density.

Main Results:

• The synthesized CPAN-PEM-2.5 membrane exhibited excellent ion-exchange capacity (1.49 meq g⁻¹) and ionic conductivity (10.49 × 10⁻² S cm⁻¹).
• Low vanadium crossover (4.09 × 10⁻⁷ cm² min⁻¹) and high ionic selectivity (2.56 × 10⁵ S min cm⁻³) were achieved due to the dual-functional architecture.
• The VRFB using CPAN-PEM-2.5 demonstrated superior electrochemical efficiency (98.60% coulombic, 76.08% voltage, 75.02% energy at 120 mA cm⁻²) and capacity retention (48.78% up to 175 cycles).
• Compared to Nafion-117, the CPAN-PEM-2.5 membrane showed higher peak power density (449.34 mW cm⁻²).

Conclusions:

• The developed PAN-based crosslinked PEM offers a promising solution for suppressing vanadium ion crossover.
• The membrane's balanced properties contribute to superior electrochemical performance and long-term stability in VRFBs.
• This novel PEM is a strong candidate for advancing grid-scale VRFB systems.