Researchers have identified a glow-in-the-dark dye as optimal material to develop batteries for energies like wind and solar in the continued quest to develop storage for large-scale alternative energy reuse.
A team of chemists at the University at Buffalo have discovered that a fluorescent dye called BODIPY -- an acronym for boron-dipyrromethene -- executes two energy-related tasks extremely well: storing electrons and participating in electron transfer. These are exactly the tasks batteries must perform to save and deliver energy, they said, making BODIPY a perfect material to store large amounts of energy in rechargeable, liquid-based batteries that could one day power cars and homes.
Anjula Kosswattaarachchi, a PhD candidate in chemistry at the University at Buffalo, holds a volumetric flask containing a glow-in-the-dark dye called BODIPY that can be used for energy storage. (Source: Douglas Levere, University at Buffalo)
Researchers tested BODIPY in what’s called a redox flow battery, which consists of two tanks of fluids separated by various barriers. Flow batteries are one method being pursued by a number of researchers as candidates for large-scale solar- and wind-energy storage. Researchers think these types of batteries will solve the problem of scale and reuse because they can easily be enlarged to store more energy for reuse later in both residential scenarios and for use by energy utilities.
“A flow battery using BODIPY can be used to store any energy source that drives the generation of electricity,” explained Timothy Cook, an assistant professor of chemistry at the University at Buffalo and the leader of the research team. “For example, a solar panel can generate a current and voltage that can be used to charge up the BODIPY dye, but the same battery could easily be attached to a wind turbine, a hydroelectric dam, or even a hand-crank generator. As long as a high enough charging voltage can be created, any source capable of generating electricity can be stored.”
The effectiveness of a redox flow battery depends on the chemical properties of the fluids in each tank. When the battery is being used, electrons are harvested from one tank and moved to the other, generating an electric current that in theory can power from the smallest device to an entire house. To recharge the battery, a solar or wind energy source would force the electrons back into the original tank, where the process of generating an electric current starts over.
Cook’s team filled both tanks of their experimental battery with the same solution -- a powdered BODIPY dye called PM 567 dissolved in liquid. Indeed, the ability to use of the same material, or “molecule,” as Cook calls it, on both sides of the battery is a benefit of the design, avoiding potential battery failure that comes when two different molecules are used, he said.
“Many other batteries use one type of molecule to give up an electron, and a second to gather these electrons,” Cook explained. “The problem with that design is that the membrane that separates the two sides of the batteries never quite keeps the two sides apart, as it must allow for molecules to pass through to balance charge. As a result, the two sides of the batteries can mix, and eventually cause the battery to fail.”
In experiments the battery maintained its high performance even after researchers drained it and recharged it 100 times, they said. Researchers published a paper on their work in a recent issue of the journal, ChemSusChem.
Cook said his team will continue to explore the use of molecules that have “promising electrochemistry for energy storage,” including molecules that can give up or accept more than one electron, and molecules that have structural properties that provide a high degree of stability once charged. Researchers also will continue their work to find ways to make other components of flow batteries, such as the separator membrane, perform better, he added.
“The key parameters of an effective flow battery are the amount of energy that can be stored, how fast you can get this energy out (commonly associated with the “power” of the battery), how compact the device can be, and how many times you can charge/discharge the battery,” Cook said. “We have ways of understanding all of these processes on the molecular level, and so by carrying out our experiments, we can get clues about how to rationally design the next generation of molecules to make better and better batteries.”
Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years. She has lived and worked as a professional journalist in Phoenix, San Francisco, and New York City. In her free time she enjoys surfing, traveling, music, yoga, and cooking. She currently resides in a village on the southwest coast of Portugal.