Harvard scientists have identified a new class of high-performing organic molecules, inspired by vitamin B2, that can safely store electricity from energy sources like solar and wind power in large batteries.
The development builds on previous work in which the team developed a high-capacity flow battery that stored energy in organic molecules called quinones and a food additive called ferrocyanide.
That advance was a game-changer, delivering the first high-performance, non-flammable, non-toxic, non-corrosive, and low-cost chemicals that could enable large-scale, inexpensive electricity storage.
While the versatile quinones show great promise for flow batteries, researchers continued to explore other organic molecules in pursuit of even better performance.
"After considering about a million different quinones, we have developed a new class of battery electrolyte material that expands the possibilities of what we can do," said Kaixiang Lin, a PhD student at Harvard University.
"Its simple synthesis means it should be manufacturable on a large scale at a very low cost, which is an important goal of this project," said Lin.
Flow batteries store energy in solutions in external tanks - the bigger the tanks, the more energy they store.
In 2014, researchers at Harvard replaced metal ions used as conventional battery electrolyte materials in acidic electrolytes with quinones, molecules that store energy in plants and animals.
Last year, they developed a quinone that could work in alkaline solutions alongside a common food additive.
In the current research, the team found inspiration in vitamin B2, which helps to store energy from food in the body.
The key difference between B2 and quinones is that nitrogen atoms, instead of oxygen atoms, are involved in picking up and giving off electrons.
"With only a couple of tweaks to the original B2 molecule, this new group of molecules becomes a good candidate for alkaline flow batteries," said Michael J Aziz, professor at the Harvard John A Paulson School of Engineering and Applied Sciences (SEAS).
"They have high stability and solubility and provide high battery voltage and storage capacity. Because vitamins are remarkably easy to make, this molecule could be manufactured on a large scale at a very low cost," said Aziz.
"We designed these molecules to suit the needs of our battery, but really it was nature that hinted at this way to store energy," said Roy Gordon, also a professor at Harvard.
"Nature came up with similar molecules that are very important in storing energy in our bodies," he said.
The research was published in the journal Nature Energy.
