By modifying the structures of molecules used in the positive and negative electrolyte solutions, and making them water soluble, the team at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) was able to produce a battery that loses only one percent of its capacity per 1000 cycles.
Flow batteries store energy in liquid solutions in external tanks -- the bigger the tanks, the more energy they store -- and are a promising storage solution for renewable, intermittent energy like wind and solar. However, current flow batteries often suffer degraded energy storage capacity after many charge-discharge cycles, requiring periodic maintenance of the electrolyte to restore the capacity. A low maintenance, long term energy storage system would change the economics of renewable energy.
"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."
This reduction of cost is important. The Department of Energy (DOE) in the US has set a goal of building a battery that can store energy for less than $100 per kilowatt-hour, which would make stored wind and solar energy competitive to energy produced from traditional power plants.
"If you can get anywhere near this cost target then you change the world," said Michael Aziz, the Gene and Tracy Sykes Professor of Materials and Energy Technologies. "It becomes cost effective to put batteries in so many places. This research puts us one step closer to reaching that target."