Engineering 101

Don’t Fear These Zombies [They’re Only Here to Help Your Batteries]

By Dawn Allcot

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The answer is: Zombies.

Working to figure out how to keep decomposing molecules from shortening the overall lifespan of an organic aqueous flow battery, Harvard University researchers discovered that creating zombies is the answer.

Before you pull out your shovel, chainsaw, and bug-out bag, they are referring to zombie molecules or molecules that actually reverse their decomposition process under certain conditions.

The research team, led by Michael Aziz, the Gene and Tracy Sykes Professor of Materials and Energy Technologies at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and Roy Gordon, the Thomas Dudley Cabot Professor of Chemistry and Professor of Materials Science, discovered how to mitigate and, ultimately, reverse the decomposition of molecules in flow batteries to prolong the battery’s overall lifespan.

The death-defying molecule, named DHAQ in the research paper but dubbed the “zombie quinone” in the lab, is among the cheapest to produce at large scale. The team’s rejuvenation method cuts the capacity fade rate of the battery at least a factor of 40, while enabling the battery to be composed entirely of low-cost chemicals.

Roy Gordon called the discovery “a major step forward in enabling us to replace fossil fuels with intermittent renewable electricity.”

Since 2014, Aziz, Gordon, and the team have been pioneering the development of safe and cost-effective organic aqueous flow batteries for storing electricity from intermittent renewable sources like wind and solar. Their batteries use molecules known as anthraquinones, which are composed of naturally abundant elements such as carbon, hydrogen, and oxygen, to store and release energy.

The researchers originally attributed the lifetime of the molecules to how many times the battery was charged and discharged, like in solid-electrode batteries such as lithium ion. However, in reconciling inconsistent results, the researchers discovered that these anthraquinones are decomposing slowly over time, regardless of how many times the battery has been used. The extent of the decomposition was based on the calendar age of the molecules, not how often they’ve been charged and discharged.

The researchers found two techniques to avoid that chain reaction: exposing the molecule to oxygen and avoiding overcharging the battery. Combining these methods to create “zombie molecules” can extend the lifespan of flow batteries, promoting the use and viability of wind and solar power by using the batteries to store energy and then deliver that energy as needed.

 

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