Dartmouth Engineer - The Magazine of Thayer School of EngineeringDartmouth Engineer - The Magazine of Thayer School of Engineering

Building a Better Battery for the Next Frontier

Thayer School has long had a reputation for engineering in the Arctic. Professor Weiyang (Fiona) Li is working on a new battery for a much colder place—the far reaches of the solar system. 

By Lee Michaelides
Photo Illustration by Adam Makarenko

Sphere Probe
Photo illustration by Adam Makarenko.

Low ion mobility—anyone who has encountered the frigid winters up north has experienced it.

It’s what happens when batteries get extremely cold. Low ion mobility—or the slow-down of electrochemical activity inside a battery—is the reason your car has trouble starting on a cold morning and why a cell phone suddenly powers down during a frosty winter walk.

Professor Weiyang (Fiona) Li, whose research focuses on renewable energy and energy storage systems, understands this phenomenon well. Her ongoing efforts to develop longer-lasting, high-efficiency batteries for extremely cold temperatures has the potential for huge impact—not just in how we power our lives here on Earth, but also for the far reaches of outer space.

Weiyang (Fiona) Li
Photograph by Robert Gill.

Li is one of 11 early-career faculty selected by NASA last year to develop innovative, early-stage technology to support the needs of the nation’s space program. “The Space Technology Research Grant Early Career Faculty Awards are one of our favorite ways at NASA to use the innovative minds in academia to help solve our high-priority technology challenges,” says Jim Reuter, acting associate administrator for NASA’s Space Technology Mission Directorate in Washington, D.C. “I’m excited to see how they advance these technologies.”

Now in the second year of a three-year, $600,000 grant, Li is exploring new battery chemistries that provide energy for future spacecraft travel to the surface of Mars or the edges of the solar systems in sub-zero temperatures.

While temperatures in space dip far below those in the coldest parts of Earth—up to hundreds of degrees Celsius below zero—for the purposes of the grant, NASA requires an energy storage system that can function at negative 40 to 80 degrees Celsius. 

“We proposed a new sodium-based battery that we hope will work well under low temperatures,” says Li. “How do we improve kinetics under such extreme temperatures? That’s the puzzle we have to solve.”

While NASA does not expect a Mars Rover-ready battery to come out of Li’s lab, she hopes to demonstrate by the end of the project how a sodium-based energy storage system can work on a small scale.

“Because this is a completely new system, there won’t be a full prototype, but there will be a small battery assembly from our lab that we test at very low temperature,” Li says. “We start with small coin-cells, like you can buy at the supermarket, to see if they function in extremely cold temperatures,” says Li. 

For the ongoing tests, Li installed in her lab an environmental chamber that can drop to negative 85 degrees Celsius. If her research is successful, the next step will be building a larger, higher-capacity, sodium-ion battery.

“For the future, we need to scale this up,” Li says. “A bigger size will present a lot of challenges. For now, NASA is more interested in the material development and a fundamental kinetic study of the chemistry.”

Why sodium? When you are looking for a solution that’s “dirt cheap,” you start with what’s already abundant in dirt, Li says. Compared to lithium, sodium is a far more accessible and plentiful element in the earth, and has a specific capacity 12 times higher than lithium. 

In addition, the cost of lithium is more prohibitive, especially on a large scale. During the past two years, lithium prices have jumped from $5,000 to $14,000 per ton. The cost of sodium: about $150 per ton. And in some studies, sodium was shown to have superior performance in cold environments.

Even with these benefits, sodium-based batteries still face hurdles—such as the growth of sodium dendrites inside the battery. Dendrites are sharp, needle-like chemical structures that grow from the anode and can puncture the separation between the anode and cathode. When the dendrite touches the cathode, it causes a short circuit that can cause the battery to overheat, explode, or catch fire. Dendrites are why some current generations of lithium batteries—which power everything from Tesla cars to laptops and cell phones—have burst into flames. 

One promising path toward solving the dendrite problem involves coating anodes with nano-scaled layers of graphene. The results from the lab have been encouraging.

“We believe this could be a viable route toward high-energy, sodium-based battery systems, and can also provide valuable insights into lithium batteries,” Li says. 

Li’s work also has far-reaching implications for cold regions closer to home. With climate crises, particularly in the Artic, where scientists have observed the most alarming impact of global heating, there is an urgent need for renewable energy and sustainable energy storage solutions to minimize further catastrophic impact. 

While energy from renewable sources such as wind and solar remain some of the most Earth-friendly solutions to curbing greenhouse gas emissions, the energy generated still requires viable battery and energy storage systems to effectively deliver and power vehicles, homes, or appliances.

Rechargeable batteries capable of withstanding extreme temperatures and other conditions are key to facilitating technology to implement renewable energy use on a more a sustainable and scalable level. 

At Dartmouth, Li, along with Assistant Professor of Chemistry Katherine Mirica, Associate Professor of Engineering Amro Farid, and Sherman Fairchild Professor of Engineering Ian Baker, have teamed up with the Arthur Irving Institute for Energy and Society at Dartmouth and researchers at the U.S. Army Corps of Engineers’ Cold Regions Research and Engineering Laboratory to develop energy storage solutions for extremely cold environments.

Funded by the U.S. Department of Defense, this project will initially look at and propose novel, high-energy lithium battery solutions for the military units based in the Arctic and other cold regions. The goal is to extend the Army’s mission capabilities by up to 30 percent while providing the next generation of energy-efficient delivery and energy storage systems.

The outcomes of this project also have far-reaching applications beyond the military. The solutions have the potential to provide communities in the Arctic and polar regions currently contending with the catastrophic effects of global warming with renewable energy storage solutions and energy-efficient power delivery systems.

Li arrived at Thayer School in 2015 as a research scientist, before joining the faculty as an assistant professor in January 2016. More recently, she was named the inaugural chair of the William P. Harris Career Development Assistant Professorship, a distinction reserved for promising faculty in their early careers.

She earned her bachelor of science and master of science degrees in chemistry from Nankai University in China and a doctorate in biomedical engineering from Washington University in St. Louis, Mo. Prior to her work at Dartmouth, she spent four years as a postdoctoral fellow at Stanford, working on energy storage and battery systems in the university’s materials sciences department. She holds three Chinese and one American patent. 

Li was attracted to Thayer’s unique approach to cross-departmental learning and research and its strength in bioengineering. 

“I appreciate the interdisciplinary collaboration, and I was also really attracted to how biomedical engineering and energy and chemistry could work together closely in the same space,” she says. 

The intersection of biomedical engineering and her work with batteries points to another future avenue of research for her lab—improving the batteries used in implantable devices. 

“There is a lot of uncertainty about the future,” Li says. “What is certain is that we are working hard to make sure we can develop batteries and energy storage systems that help deliver energy to some of the coldest parts of Earth and even to space. It’s a very exciting to part of the solution.”

Lee Michaelides is a contributing editor of Dartmouth Engineer.

Categories: Features

Tags: climate change, energy, energy storage, innovation, NASA, research

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