New organic molecule stores twice the energy and retains 99% capacity after nearly 200 cycles

A collaborative research team from the Université de Montréal and Concordia University has unveiled a breakthrough organic molecule that could solve the intermittency challenges of renewable energy. Dubbed "AzoBiPy" (formally 4,4′-hydrazobis(1-methylpyridinium)), the molecule is designed for use in aqueous organic redox flow batteries (AORFBs) — a safer, non-flammable alternative to lithium-ion systems.

The findings — published in the Journal of the American Chemical Society — highlight AzoBiPy's ability to undergo a reversible two-electron transfer. While most organic posolyte (positive electrolyte) molecules only exchange a single electron, AzoBiPy doubles this capacity.

In laboratory tests, the molecule demonstrated a high volumetric specific capacity of 47.1 Ah/L and exceptional solubility in water.

Stability has long been the weakness of organic storage, but AzoBiPy set a new benchmark. During a 70-day trial involving 192 charge-discharge cycles, the molecule retained nearly 99% of its initial capacity, losing a mere 0.02% per day. Researchers say this performance is almost unprecedented for an organic compound, suggesting it could store energy collected in the summer to heat homes throughout the winter.

The practical potential of this technology was highlighted during a 2024 live demonstration at a departmental holiday event. A prototype flow battery, using only two tablespoons of the aqueous solution per tank, successfully powered a set of Christmas tree lights for eight hours.

Renewability-wise, while commercial flow batteries rely mostly on vanadium, AzoBiPy is composed of abundant elements like carbon, nitrogen, and hydrogen. The team is currently exploring bio-based versions derived from wood and food waste. With patent applications underway, the researchers expect this class of compounds to reach wide-scale adoption within the next decade or so.