A common food and medicine additive has shown it can boost the capacity and longevity of a next-generation flow battery design in a record-setting experiment. A research team from the Department of Energy’s Pacific Northwest National Laboratory reports that the flow battery, a design optimized for electrical grid energy storage, maintained its capacity to store and release energy for more than a year of continuous charge and discharge.
Flow batteries provide long-lasting, rechargeable energy storage, particularly for grid reliability. Unlike solid-state batteries, flow batteries store energy in liquid electrolyte, shown here in yellow and blue. Researchers at PNNL developed a cheap and effective new flow battery that uses a simple sugar derivative called β-cyclodextrin (pink) to speed up the chemical reaction that converts energy stored in chemical bonds (purple to orange), releasing energy (electrons) to power an external circuit. A parallel reversible process (red-green) in the positive catholyte solution balances the positive and negative charges during charge and discharge.
The study, just published in the journal Joule, details the first use of a dissolved simple sugar called β-cyclodextrin, a derivative of starch, to boost battery longevity and capacity.
In a series of experiments, the scientists optimized the ratio of chemicals in the system until it achieved 60 percent more peak power. Then they cycled the battery over and over for more than a year, only stopping the experiment when the plastic tubing failed. During all that time, the flow battery barely lost any of its activity to recharge. This is the first laboratory-scale flow battery experiment to report more than a year of continuous use with minimal loss of capacity.
The β-cyclodextrin additive is also the first to speed the electrochemical reaction that stores and then releases the flow battery energy, in a process called homogeneous catalysis. This means the sugar does its work while dissolved in solution, rather than as a solid applied to a surface.
“This is a brand new approach to developing flow battery electrolyte,” said Wei Wang, a long-time PNNL battery researcher and the principal investigator of the study. “We showed that you can use a totally different type of catalyst designed to accelerate the energy conversion. And further, because it is dissolved in the liquid electrolyte it eliminates the possibility of a solid dislodging and fouling the system.”
While there are many flow battery designs and some commercial installations, existing commercial facilities rely on mined minerals such as vanadium that are costly and difficult to obtain. That’s why research teams are seeking effective alternative technologies that use more common materials that are easily synthesized, stable and non-toxic.
“We cannot always dig the Earth for new materials,” said Imre Gyuk, Director of energy storage research at DOE’s Office of Electricity. “We need to develop a sustainable approach with chemicals that we can synthesize in large amounts — just like the pharmaceutical and the food industries.”
The work on flow batteries is part of a large program at PNNL to develop and test new technologies for grid-scale energy storage that will be accelerated with the opening of PNNL’s Grid Storage Launchpad in 2024.
The PNNL research team that developed this new battery design includes researchers with backgrounds in organic and chemical synthesis. These skills came in handy when the team chose to work with materials that had not been used for battery research, but which are already produced for other industrial uses.
“We were looking for a simple way to dissolve more fluorenol in our water-based electrolyte,” said Ruozhu Feng, the first author of the new study. “The β-cyclodextrin helped do that, modestly, but it’s real benefit was this surprising catalytic ability.”
The research team has applied for U.S. patent protection for their new battery design.
For more information, contact Karyn Hede at