Optimized Sulfonated Poly(Ether Ether Ketone) Membranes for In-House Produced Small-Sized Vanadium Redox Flow Battery...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Ionic exchange membranes are critical for redox flow battery (VRFB) performance, durability, and cost.
• Optimizing membrane properties and electrolyte composition is key to enhancing VRFB efficiency.

Purpose of the Study:

• To optimize lab-scale VRFB operating conditions for membrane physicochemical features and electrolyte composition.
• To translate these optimized conditions to a large-scale five-cell VRFB stack.

Main Methods:

• Investigated sulfonated poly(ether ether ketone) (SPEEK) membranes with varying sulfonation degrees (SD) and fillers.
• Compared SPEEK membranes against commercial Nafion 115.
• Evaluated chloride-based electrolytes against standard sulfuric acid electrolytes.

Main Results:

• SPEEK50-0 (50% SD, 0% filler) showed high permeability and selectivity for vanadium.
• SPEEK50-0 with a chloride electrolyte achieved 93.4% coulombic efficiency, outperforming Nafion 115 (88.9%) in a single-cell VRFB.
• Optimized conditions were successfully scaled to a five-cell VRFB stack, reaching 94.5% coulombic efficiency.

Conclusions:

• SPEEK50-0 is a promising, cost-effective membrane material for VRFBs.
• Chloride-based electrolytes enhance VRFB performance when paired with optimized SPEEK membranes.
• The study successfully demonstrated the scalability of optimized VRFB components for practical energy storage.