Over the last 30 years, rechargeable lithium-ion batteries have gotten smaller and more powerful, making them key components in smartphones, laptops, earbuds, electric cars and just about every portable electronic device.
The next generation of battery-powered technologies, however, will require more power, increased longevity and better stability than lithium-ion can provide. That’s why Matthew Gebbie, Conway Assistant Professor in the Department of Chemical and Biological Engineering at the University of Wisconsin-Madison, will use a three-year Early Career Program award from the Army Research Office, a directorate of the U.S. Army Combat Capabilities Development Command Army Research Laboratory, to research ionic liquid electrolytes for new battery chemistries.
The research could lead to lighter, safer, more energy-dense batteries, which would greatly benefit soldiers, especially in remote areas or in harsh conditions.
Researchers are looking at ions to replace lithium in batteries—in particular, multivalent ions like magnesium, calcium, zinc, and aluminum, which are capable of carrying more energy per ion moved within devices. One major hurdle, however, is poor performance of organic liquid electrolytes used in lithium-ion batteries, the materials that transport charged ions between the positive and negative terminals. These liquids are unstable and can lead to fires and explosions if exposed to harsh conditions. They’re even less stable when used with multivalent ions.
“There’s a big issue with the safety profile of these organic electrolytes,” says Gebbie. “This is a major challenge when you start thinking about soldiers, who typically carry packs greater than 100 pounds in weight. A lot of that weight is batteries, and soldiers often deploy to extreme environments, whether it’s the desert, where temperatures are high, or the Arctic, with extremely low temperatures.”
Gebbie and his students are investigating new types of electrolytes made of nanostructured ionic liquids customized to handle different multivalent ions, each of which has very different properties than lithium. “We really need to invent new electrolytes, and we’re trying to build out the core materials science to determine whether these materials can enable next-generation batteries,” he says.
A lot of recent research has focused on solid ceramic electrolytes, which are much more stable than organic liquids and mitigate flammability. Yet multivalent ions tend to get stuck in these materials. The ionic liquids Gebbie is working with, however, offer a compromise. At the molecular level, the compounds they are investigating don’t fit easily into the definition of a traditional brittle solid or unstructured liquid. By balancing molecular level interactions, the Gebbie lab is aiming to create materials with the stability of solid electrolytes, while still allowing multivalent ions to flow the way they do in liquid electrolytes.
They have other advantages as well. Gebbie says that fine-tuning the electrolytes could open the door to multiple types of battery chemistries, suited for different applications. Not only could these new types of batteries be safer and more powerful, they could also alleviate geopolitical problems associated with components of lithium-ion batteries, which are increasingly scarce and involve overseas supply chains. In contrast, batteries based on magnesium, zinc and aluminum often leverage chemistries that promise to become much cheaper and more widely available.
Gebbie says much of the preliminary work for this project was funded by a Wisconsin Alumni Research Foundation Electrification Challenge seed grant. Now, working with the Army Research Office, he’s hoping to make these electrolytes a reality. “We’re excited about getting involved and engaged in this community of scientists and leaders in the field of energy storage.” he says, “I am also enthusiastic about educating students and contributing to the development of a domestic workforce that’s going to go forward and help us innovate in electrochemical science.”
Featured image caption: Assistant Professor Matt Gebbie and graduate student Ryan Cashen are studying new electrolytes for stable, long-lasting batteries.