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A Protocol for Electrochemical Evaluations and State of Charge Diagnostics of a Symmetric Organic Redox Flow Battery
Published on: February 13, 2017
A Zwitterionic Azo Posolyte for Long-Lifetime Aqueous Redox Flow Batteries
Zhiyu Wang1, Xun Wang1, Manohar Salla1
1Center for Research on Energy Systems and Technologies (CREST), Department of Materials Science and Engineering, College of Design and Engineering, National University of Singapore, Singapore, Singapore.
Advanced Materials (Deerfield Beach, Fla.)
|August 6, 2026
Summary
A new azo-based molecule (ABPS) significantly improves aqueous organic redox flow batteries (AORFBs) for grid storage. This zwitterionic compound offers high solubility, stability, and capacity, addressing key challenges in energy storage technology.
Area of Science:
- Electrochemistry
- Materials Science
- Renewable Energy Storage
Background:
- Variable renewable energy sources necessitate efficient, long-duration grid-level energy storage solutions.
- Aqueous organic redox flow batteries (AORFBs) present a promising avenue due to tunable chemistry and scalable architecture.
- Developing stable, high-performance posolytes (positive electrode solutions) is critical for AORFB advancement.
Purpose of the Study:
- To design and synthesize a novel posolyte molecule for acidic AORFBs that overcomes limitations in redox potential, solubility, capacity, and stability.
- To evaluate the electrochemical performance and long-term cycling stability of the new molecule in both symmetric and full cell configurations.
- To demonstrate a viable molecular design strategy for durable, high-power AORFB applications.
Main Methods:
- Synthesis and characterization of a zwitterionic azo-based molecule, 4,4'-azo-bis(1-pyridinium-3-propane-sulfonate) (ABPS).
- Electrochemical testing in symmetric and full cells using acidic electrolytes (2.0 M H2SO4).
- Long-term cycling stability tests to assess capacity fade and coulombic efficiency.
Main Results:
- ABPS exhibits high water solubility (1.30 M) and intrinsic zwitterionic character, reducing molecule crossover.
- Symmetric cell cycling demonstrated exceptional stability over 3800 cycles (99.98% average coulombic efficiency, 0.198% year-1 capacity loss).
- Full cell tests with V2+/3+ yielded a high voltage (1.14 V), capacity density (48.5 Ah L-1), and ultralow capacity decay (0.084% year-1 over 1100 h).
Conclusions:
- The rational design of azo-based zwitterionic structures provides a robust pathway for developing high-performance, stable posolytes for acidic AORFBs.
- ABPS demonstrates significant potential for low-cost, long-duration grid-scale energy storage.
- This molecular design approach offers a universal strategy for enhancing AORFB durability and power.
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