One of the biggest challenges facing renewable energy is timing. Wind turbines and solar panels often produce electricity when it is not immediately needed.
A sunny summer afternoon can generate far more power than households use, while cold winter nights demand energy when the sun and wind may be scarce.
Storing that excess electricity for long periods has remained a major obstacle—until now.
Chemists at Université de Montréal, working with colleagues at Concordia University, have developed a new organic molecule that can store electrical energy for months with almost no degradation.
The molecule, called AzoBiPy, held its charge with exceptional stability during long-term testing, offering a promising path toward better large-scale energy storage. The findings were published in the Journal of the American Chemical Society.
The research team tested AzoBiPy inside a redox flow battery for 70 days. Over that time, the molecule lost just 0.02 percent of its energy capacity per day.
By the end of the experiment, it still retained nearly 99 percent of its original charge. In addition, AzoBiPy can store roughly twice as much energy as many similar organic molecules and dissolves easily in water, both key advantages for large storage systems.
The goal of the project is to help solve the problem of renewable energy intermittency, which limits how much solar and wind power can be integrated into electricity grids.
Flow batteries offer a different approach from familiar batteries like those in phones or electric vehicles. In conventional batteries, energy is stored directly inside solid electrodes. In contrast, redox flow batteries store energy in liquid solutions held in external tanks.
In a flow battery, two tanks hold water-based electrolyte solutions containing energy-storing molecules. These liquids are pumped through a central cell where they exchange electrons through a membrane without mixing. The larger the tanks, the more energy the system can store, while the power output depends on the size of the cell. This separation makes flow batteries especially attractive for large-scale, stationary energy storage.
Today’s commercial flow batteries usually rely on vanadium, a metal with excellent electrochemical properties but limited availability and high cost.
The new work replaces metal-based materials with organic molecules made from common elements such as carbon, hydrogen, nitrogen, and oxygen. AzoBiPy belongs to a class of molecules designed to move electrons efficiently while remaining chemically stable.
One of AzoBiPy’s most important features is its ability to exchange two electrons instead of one. This allows each molecule to store twice as much energy, significantly improving battery capacity.
Stability, however, has long been the weak point of organic molecules in flow batteries. Many degrade after repeated charging cycles. AzoBiPy performed unusually well, surviving nearly 200 full charge–discharge cycles with minimal loss.
The researchers even demonstrated the technology at a holiday event by powering Christmas lights for eight hours using a small prototype battery filled with just a few tablespoons of liquid.
Because the system is water-based, it is non-flammable, making it safer than lithium-ion batteries for large installations.
Looking ahead, flow batteries using molecules like AzoBiPy could store electricity from solar and wind farms and release it during peak demand.
Smaller versions could one day provide safer, greener energy storage for homes. The team is now expanding the work to develop a whole family of similar molecules and believes the technology could see widespread use within the next decade or two.
Source: University of Montreal.
