Understanding molecules in new detail yields better materials
Dept. of Chemistry/UIUC
Joaquín Rodríguez-López, 35
University of Illinois at Urbana-Champaign
Today, he’s tackling one big obstacle to expanding affordable renewable energy on the U.S. electrical grid: storage. The flow batteries that store large amounts of energy generated by wind and solar power need to more efficiently hold that energy for times when the sun isn’t shining or the breeze dies down.
In his laboratory at the University of Illinois at Urbana-Champaign, Rodríguez-López, 35, has designed a new type of material to store electric charge in these batteries, making them more efficient. And he’s not stopping there. “We design new ways of looking at materials, and we design better materials,” he says.
His collaborator at the University of Illinois, Jeffrey Moore, praises his “deep knowledge and … willingness to share it.” Rodríguez-López has always had a community-focused mindset. Growing up in Mexico, he entertained himself for hours at home with Encyclopedia Britannica. But at school, he says, he’d hang around with kids who weren’t doing as well academically. He liked helping them out.
Today, he’s still drawn to collaboration, working with Moore and others via the Joint Center for Energy Storage Research, an initiative funded by the U.S. Department of Energy to bring new battery and fuel cell technology from research labs to commercialization.
“He’s really shown an ability to get a team working together toward a common goal,” Moore says.
An important goal for materials science today is to build better batteries (SN: 1/21/17, p. 22). The ubiquitous lithium-ion battery adeptly powers cell phones and laptops, but it’s not necessarily the best way to store the large quantities of energy generated by wind turbines or solar panels, Rodríguez-López says. So a major focus in his lab has been on bettering the flow battery.
A flow battery has two big tanks loaded with solutions, one positively charged and one negatively charged. The tanks are separated by a membrane, where the two solutions meet and undergo chemical reactions that generate a flow of electrons, or electric current. To make a lithium-ion battery store more electric charge requires scaling up its positively and negatively charged electrode
s, which are made of expensive materials. But to scale up a flow battery, just increase the size of the tanks of liquid for not much more cost.
“Instead of having big electrodes, you have big tanks,” says Rodriguez-López. It’s a simpler way to store a large amount of power generated by wind or solar for later use.
Joaquín Rodríguez-López and colleagues have designed polymers too big to seep through the membrane between a flow battery's positively and negatively charged solutions, so the battery doesn’t waste energy.
Source: G. Nagarjuna et al/J. Am. Chem. Soc. 2014
But in today’s flow batteries the reaction-driving particles sometimes leak across the membrane, wasting energy. Rodríguez-López and colleagues have designed a new kind of bulky particle that still dissolves well in liquid but can’t cross the barrier. These polymers, described in 2014 in the Journal of the American Chemical Society, link dozens or even hundreds of smaller units in an array of shapes. The particles store and discharge electric energy in the battery through a series of chemical reactions that progress along the polymer unit by unit, like a flame moving up a match.
When Rodríguez-López began this research a few years ago, it was a side project for the Joint Center for Energy Storage Research, where George Crabtree, a materials scientist at Argonne National Laboratory in Argonne, Ill., is director. Now, Crabtree says, thanks to Rodríguez-López, the work is a major focus of the center.
Rodríguez-López is thinking bigger than designing new materials, though. He’s also using new techniques to figure out why and how these materials behave the way they do so he can troubleshoot more rationally, and, ultimately, get the molecules to do exactly what he wants.
For example, he’s become an expert in a scanning electrochemical microscopy so he can watch electrons move as chemical reactions progress along his lengthy molecules. He uses the technique To aim for ideal properties in his batteries.
Looking forward, Rodríguez-López says he’d like to bring more biological influence into his molecule-designing work. After all, he says, cells are filled with bulky proteins finely tuned for specific jobs. Some can repair themselves when broken, for instance, while others can self-destruct. Understanding nature’s complexity, he says, could help him design materials for batteries that react in more sophisticated ways.
G. Nagarjuna et al. Impact of redox-active polymer molecular weight on the electrochemical properties and transport across porous separators in nonaqueous solvents. Journal of the American Chemical Society. October 17, 2014. doi: 10.1021/ja508482e.
M. Burgess et al. Redox Active Polymers as Soluble Nanomaterials for Energy Storage. Accounts of Chemical Research. September 27, 2016. doi:10.1021/acs.accounts.6b00341.