Leveraging Long-Life Alkaline Redox Flow Batteries Using Durable and High-Hydroxide Exchange N-Bridged Triazine...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Fluorine-free polyelectrolyte membranes are crucial for sustainable energy storage.
• Challenges exist in balancing membrane properties for long-life electrochemical devices.
• Covalent organic frameworks (COFs) offer potential but face co-precipitation issues.

Purpose of the Study:

• To design a durable, ionically miscible dual-ion exchange membrane for alkaline redox flow batteries (RFBs).
• To utilize a triazine organic framework (TOF) to overcome limitations of current membranes.
• To enhance energy efficiency, density, and power in RFBs.

Main Methods:

• Fabrication of all-hydrocarbon TOF-based polyelectrolyte membranes (sTOF's).
• Characterization of dual ion-exchange architectures and net ion-exchange capacity (>2.1 meq g⁻¹).
• Performance testing in alkaline RFBs, including efficiency, energy density, power density, and cycle life.

Main Results:

• sTOF membranes exhibit energy efficiency >80%, surpassing Nafion.
• Achieved high electrolyte utilization (≈100%) and excellent capacities.
• Demonstrated preserved efficiencies (>97%), reduced overpotentials (≤200 mV), and extended battery life.
• sTOF-5 showed superior peak power density (2.3 W) compared to Nafion-117 (1.45 W).
• Maintained >50% capacity after ≈3000 cycles, comparable to fresh Nafion-117.

Conclusions:

• The developed TOF-based PEMs offer a promising fluorine-free alternative for high-performance alkaline RFBs.
• Dual ion-exchange architecture enhances electrolyte utilization and battery longevity.
• These membranes enable higher redoxolyte concentrations, significantly boosting energy densities.