Weiyang ("Fiona") Li, the William P. Harris Career Development Assistant Professor of Engineering. (Photo by Kathryn LoConte Lapierre)

Li began to focus on battery technology during her undergraduate studies at Nankai University in China in 2003. Now, at Dartmouth, she and her team are working to develop nonflammable solid-state electrolytes—considered a promising alternative to flammable liquid electrolytes—so that when a battery short-circuits and overheats, it doesn't become a fire hazard.

Electrolytes are crucial to battery function because they facilitate the flow of electrical energy via the movement of ions. The NSF funding will enable Li and her lab group to delve more into the structure and composition of nonflammable electrolyte surface properties. The work is part of a larger effort to develop a sodium-based battery that offers important advantages over conventional lithium-ion batteries.

"The knowledge enabled by this research will stimulate the development of solid-state sodium batteries that have superior thermal and chemical stability and will serve as a new alternative low-cost power source for energy storage applications," she says.

Li says a sodium battery has plenty of advantages over a lithium one. For example, it costs an estimated 30-40% less to make a sodium battery, and sodium is more abundant and available given that it can be extracted from dirt, whereas lithium is a finite material that must be mined. These advantages are key, given the skyrocketing demand for battery-powered electric vehicles and solar and wind farms that require batteries to store a surplus of clean energy.

For these reasons, Li says, sodium-based batteries can help solve complicated energy and environmental challenges, especially in places that require more powerful, temperature-appropriate batteries. Li has already collaborated with Dartmouth's Arthur Irving Institute for Energy and Society as well as the nearby US Army Corps of Engineers' Cold Regions Research and Engineering Laboratory on the development of energy storage solutions for extremely cold environments. In the Arctic for example, where scientists continue to study the effects of climate change, there is a need for renewable energy and sustainable energy storage solutions. Li's sodium battery could one day provide people in the Arctic with energy-efficient power delivery systems.

"Lithium-ion batteries have been extensively employed in portable electronics and electric vehicles because of their ability to hold a charge for a long period of time, but they inevitably suffer severe energy and power loss in cold environments, especially when temperatures drop below minus four Fahrenheit," says Li. "This limits their applications for space missions, polar expeditions and many military and civil facilities in cold regions, where a battery operating temperature below minus 40 is typically required."

In addition to advancing battery technology, Li hopes to circulate her research findings to students across a wide range of age groups—from elementary, middle and high school students to undergrads and grad students. Specifically, she wants to integrate her research into a high school AP curriculum and develop a battery-themed summer workshop that focuses on elementary and middle school girls to help break down gender barriers.

"I plan to integrate this project into a variety of educational and outreach activities to broadly disseminate the research findings, promote diversity in engineering research and tackle the gender gap in STEM fields," Li says.

Her own path to a career in STEM began in China. After her undergraduate studies, she went on to earn a graduate degree in chemistry, also from Nankai. She then came to the US to earn a doctorate in biomedical engineering from Washington University, with the intent of merging her interests in chemistry and engineering. After spending four years as a post-doctoral fellow at Stanford, Li joined the engineering faculty at Thayer in 2016, calling the Dartmouth community "spirited, collaborative, passionate and kind."

While Li is still early in her academic career, she has plenty of accolades. She has won the Camille Dreyfus Teacher-Scholar Award (with a $100,000 research grant), and the Air Force's Young Investigator Program Award. She also received an Early Career Faculty (ECF) award from NASA's Space Technology Research Grants Program with the goal of developing technology suitable for the harsh low-temperature conditions of outer space.