Research extends lifespan of molecules in organic power batteries to practical values

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), in collaboration with colleagues from the University of Cambridge, have developed a new method to dramatically extend the life of organic aqueous power batteries, increasing the commercial viability of a technology. which has the potential to safely and cheaply store energy from renewable sources such as wind and solar.

“Organic aqueous redox flow batteries promise to significantly reduce the cost of electricity storage from intermittent energy sources, but the instability of the organic molecules has hindered their commercialization,” said Michael Aziz, the Gene and Tracy Sykes Professor of Materials and Energy Technologies at SEAS. “Now we have a really practical solution to extend the life of these molecules, which is a huge step in making these batteries competitive.”

The research is published in Nature Chemistry.

Over the past decade, Aziz and Roy Gordon, the Thomas Dudley Cabot Professor of Chemistry and Professor of Materials Science, have collaborated to develop organic aqueous flow batteries using molecules known as anthraquinones, which are composed of naturally occurring elements such as carbon, hydrogen, and oxygen, to store and release energy.

In the course of their research, the team found that these anthraquinones slowly decompose over time, regardless of how many times the battery has been used.

In previous work, the researchers found that they could extend the lifespan of one of these molecules, called DHAQ, but dubbed the “zombie quinone” in the lab by exposing the molecule to air. The team found that when the molecule is exposed to air at just the right part of its charge-discharge cycle, it grabs oxygen from the air and turns back into the original anthraquinone molecule — as if returning from the dead, hence its nickname.

But regularly exposing a battery’s electrolyte to air isn’t really practical, because it throws the two sides of the battery off balance – both sides of the battery can no longer be fully charged at the same time.

To find a more practical approach, the researchers teamed up with chemists from the University of Cambridge in the UK to better understand how the molecules decompose and devised an electrical method to reverse the process.

The team found that if they performed a so-called deep discharge, which drains the positive and negative terminals of the battery so that the voltage difference between the two becomes zero, then the battery’s polarity reverses, forcing the positive side to negative and the negative side positive, it created a voltage pulse that could return the decomposing molecules to their original shape.

“Usually when using other types of batteries, you want to avoid completely draining the battery because it tends to degrade the components,” said Yan Jing, a Harvard postdoctoral researcher and co-first author of the paper. “But we’ve found that this extreme discharge, until the polarity actually reverses, can reassemble these molecules — which was a surprise.”

The process works a bit like a pacemaker, periodically shocking the system that revives broken down molecules.

In this article, the researchers showed a net lifespan of 17 times longer than previous research. In subsequent studies, which refined the process, the researchers showed an even greater increase in lifespan, up to 260 times longer, leading to a loss rate of less than 10% per year. That research has yet to be published.

“If we get to a loss rate of one digit per year, then widespread commercialization is really possible, because it’s not a huge financial burden to replenish your tanks by a few percent every year,” Aziz says.

Harvard’s Office of Technology Development has protected the intellectual property of this project and has licensed the technology and other related patents on quinone power batteries to Quino Energy, a startup pursuing its commercial development.

The research team also showed that this approach works for a range of organic molecules and for a range of deep discharge processes, both with and without polarity reversal. Next, the team wants to investigate to what extent they can extend the lifespan of DHAQ and other low-cost anthraquinones used in these systems.

“Flow batteries are expected to be the next wave in storage technology next to lithium — specifically batteries with organic electrolytes,” said Imre Gyuk, director of the Department of Energy’s Office of Electricity Storage program. “This work allows control over the decomposition process, significantly extending lifespan and enabling medium and long-term energy storage applications.”

The study was co-authored by Evan Wenbo Zhao, Marc-Antoni Goulet, Meisam Bahari, Eric M. Fell, Shijian Jin, Ali Davoodi, Erlendur Jónsson, Min Wu, Clare P. Gray, and Roy G. Gordon. It was supported by the US National Science Foundation through grant CBET-1914543, by US DOE award DE-AC05-76RL01830 through PNNL subcontract 535264, and by a grant from the Massachusetts Clean Energy 393 Center.


  1. Yan Jing, Evan Wenbo Zhao, Marc-Antoni Goulet, Meisam Bahari, Eric M. Fell, Shijian Jin, Ali Davoodi, Erlendur Jónsson, Min Wu, Clare P. Grey, Roy G. Gordon, Michael J. Aziz. In situ electrochemical reconstitution of decomposed redox active species in aqueous organic flow batteries. Natural Chemistry, 2022; DOI: 10.1038/s41557-022-00967-4
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