Composite Membrane for Sodium Polysulfide Hybrid Redox Flow Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Non-aqueous redox flow batteries (NARFBs) offer promising long-duration energy storage using earth-abundant materials like sodium and sulfur.
• Organic solvents in NARFBs allow higher operating voltages and energy densities than aqueous systems.
• A significant challenge for NARFBs is the lack of cost-effective membranes with sufficient ionic conductivity and selectivity.

Purpose of the Study:

• To develop and evaluate a novel composite membrane for sodium-based hybrid redox flow batteries.
• To improve the electrochemical stability and performance of membranes in NARFB systems.

Main Methods:

• Fabrication of a composite membrane using a thin Na+-Nafion coating on a porous polypropylene scaffold (<25 µm).
• Evaluation of electrochemical stability via Na symmetric cell testing.
• Assessment of ionic conductivity and mechanical properties at room temperature.

Main Results:

• The composite membrane demonstrated significantly improved electrochemical stability, with stable performance exceeding 2300 hours compared to unprotected Na+-Nafion (445 hours).
• The composite membrane exhibited enhanced room temperature storage modulus compared to its individual components.
• High Na+ conductivity of 0.24 mS/cm at 20 °C was maintained.

Conclusions:

• The developed composite membrane is a promising solution for enhancing the durability and efficiency of sodium-based hybrid redox flow batteries.
• This approach addresses critical membrane limitations, advancing the viability of NARFBs for long-duration energy storage.