Go with the Flow – Structural Modification of Molecules Promises Better Flow Batteries

Energy stored in organic molecules dissolved in neutral pH water offers increased battery life and lower costs.

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Michael J. AzizPhoto of battery (right foreground), negative electrolyte composed of ACA in alkaline solution immersed under water to keep air out (left foreground), and pumps (background).

A battery has been developed which is non-toxic and non-corrosive making it safe enough to act as an energy storage solution in homes.

Flow batteries store energy in liquid solutions in external tanks — the bigger the tanks, the more energy they store. They are a viable solution for intermittent renewable energy sources such as wind and solar.

However, frequent and long-term charge-discharge cycles can degrade storage capacity leading to periodic maintenance of the electrolyte to restore capacity.

Because we were able to dissolve the electrolytes in neutral water, this is a long-lasting battery that you could put in your basement

By modifying the structures of molecules used in the positive and negative electrolyte solutions, and making them water soluble, a team at the John A. Paulson School of Engineering and Applied Sciences (SEAS) at Harvard was able to build a battery that loses only one percent of its capacity every 1,000 cycles.

“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.”

Michael J. AzizEnergy-storing chemicals (hydroquinone/quinone and bromine/hydrobromic acid) are held in containers (background) and are pumped through the energy conversion hardware (foreground), converting chemical energy to electrical energy and vice versa. In order to store more energy, the energy conversion hardware does not need to change: only the container size and the amount of chemicals needs to increase.

The research was featured recently in ACS Energy Letters.

“This work on aqueous soluble organic electrolytes is of high significance in pointing the way towards future batteries with vastly improved cycle life and considerably lower cost,” said Imre Gyuk, Director of Energy Storage Research at the Office of Electricity of the DOE.

“I expect that efficient, long duration flow batteries will become standard as part of the infrastructure of the electric grid.”

The researchers are currently working with several companies to scale up the technology for industrial applications and to optimise the interactions between the membrane and the electrolyte.

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