A new flow battery from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) stores energy in organic molecules dissolved in neutral pH water. Losing only one percent of its capacity per 1000 cycles, the non-toxic, non-corrosive device offers the potential to significantly decrease the costs of production.
“Lithium ion batteries don’t even survive 1000 complete charge/discharge cycles,” said Michael Aziz, the Gene and Tracy Sykes Professor of Materials and Energy Technologies.
Flow batteries, a promising solution for renewable, intermittent energy like wind and solar, store energy in liquid solutions, held in external tanks. The Harvard team modified the structures of molecules used in the positive and negative electrolyte solutions, making them water soluble.
“Because we were able to dissolve the electrolytes in neutral water, this is a long-lasting battery that you could put in your basement,” said Roy Gordon, the Thomas Dudley Cabot Professor of Chemistry and Professor of Materials Science. “If it spilled on the floor, it wouldn’t eat the concrete and since the medium is noncorrosive, you can use cheaper materials to build the components of the batteries, like the tanks and pumps.”
By first identifying how the molecule viologen in the negative electrolyte was decomposing, postdoctoral fellow Eugene Beh modified and strengthened its molecular structure. Then, by functionalizing ferrocene molecules the same way as the viologen, the team was able to turn an insoluble molecule into a highly soluble one that could be cycled stably.
The Department of Energy (DOE) has set a goal of building a battery that stores energy for less than $100 per kilowatt-hour, which would make stored wind and solar energy competitive with energy produced from traditional power plants.
“If you can get anywhere near this cost target then you change the world,” said Aziz. “It becomes cost effective to put batteries in so many places. This research puts us one step closer to reaching that target.”
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