A new advance in energy storage could make renewable power far easier to rely on year-round. Researchers from the Université de Montréal and Concordia University have introduced an organic molecule designed to tackle one of clean energy’s biggest headaches: what to do when the sun isn’t shining and the wind isn’t blowing.
The molecule, called AzoBiPy (short for 4,4′-hydrazobis(1-methylpyridinium)), was created for aqueous organic redox flow batteries, also known as AORFBs. These flow batteries store energy in liquid electrolytes kept in external tanks, and unlike many conventional battery setups, they use water-based chemistry. That matters because water-based flow batteries can be safer and non-flammable, offering an appealing alternative to lithium-ion batteries for large-scale storage.
What makes AzoBiPy stand out is how efficiently it moves electrons during charging and discharging. Most organic “posolyte” molecules used on the positive side of these batteries typically transfer just one electron per cycle. AzoBiPy can reversibly transfer two electrons, effectively doubling the charge-storage capability from the same active material. In lab tests, it reached a volumetric specific capacity of 47.1 Ah/L and showed strong water solubility—two traits that are critical for practical, high-capacity redox flow battery performance.
Organic battery materials have often struggled with a major limitation: stability over time. Many promising compounds degrade too quickly to be useful for grid-scale energy storage. AzoBiPy, however, delivered unusually strong long-term results. Over a 70-day evaluation covering 192 charge-discharge cycles, it maintained nearly 99% of its original capacity, fading at only about 0.02% per day. That level of capacity retention is rare for organic compounds and points toward something renewable energy planners have long wanted—storage that can bridge not just hours or days, but potentially seasons. The researchers suggest performance like this could help store summer-generated energy for use during winter months, such as supporting home heating needs.
The technology’s real-world promise wasn’t limited to the lab. In a 2024 live demonstration at a departmental holiday event, the team showcased a prototype flow battery using just two tablespoons of the aqueous solution per tank. Even with that small amount of electrolyte, the system powered Christmas tree lights continuously for eight hours, offering a clear, memorable example of how flow battery storage can work in everyday settings.
Another advantage is materials sourcing. Many commercial redox flow batteries rely on vanadium, which can be costly and supply-constrained. AzoBiPy is built from abundant elements such as carbon, nitrogen, and hydrogen. The team is also investigating bio-based versions that could be produced using feedstocks like wood and food waste—an approach that could reduce costs further while improving sustainability.
With patent applications in progress, the researchers believe this new class of organic molecules could move toward broader adoption within roughly the next decade. If development continues on its current trajectory, AzoBiPy-powered aqueous organic redox flow batteries may become a key piece of the puzzle for reliable, safe, and scalable renewable energy storage.
