Development of efficient aqueous organic redox flow batteries using ion-sieving sulfonated polymer membranes

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aqueous organic redox flow batteries offer cost-effective grid-scale energy storage.
• Membrane cross-over of active species is a major limitation, causing performance degradation.
• Developing selective membranes is crucial for improving battery longevity and efficiency.

Purpose of the Study:

• To develop size-selective ion-exchange membranes for aqueous organic redox flow batteries.
• To address the challenge of active species crossover through membranes.
• To enhance the performance and stability of redox flow batteries.

Main Methods:

• Sulfonation of a spirobifluorene-based microporous polymer to create ion-exchange membranes.
• Characterization of membrane properties, including ion transport and molecular sieving.
• Testing membrane performance in a laboratory-scale aqueous organic redox flow battery.

Main Results:

• The developed membranes exhibit efficient ion sieving, controlling cation transport while blocking organic molecules.
• Enhanced membrane selectivity significantly reduced capacity decay caused by crossover.
• Improved ionic conductivity was maintained in aqueous electrolytes at pH 9.
• The membranes boosted energy efficiency and peak power density.
• Stable battery operation exceeding 120 hours (2100 cycles) was demonstrated.

Conclusions:

• Spirobifluorene-based membranes effectively mitigate active species crossover in aqueous organic redox flow batteries.
• These membranes improve battery stability, energy efficiency, and power density.
• The study demonstrates a viable strategy for advancing cost-effective grid-scale energy storage solutions.