A materials scientist seeks to extract lithium from untapped sources

Electric vehicles promise to help wean us off of fossil fuels, but they introduce a new problem: a approach to get enough of the lithium that EV batteries require (SN: 5/7/19).

Materials scientist Chong Liu of the University of Chicago has some ideas. Existing technology can extract lithium handiest from sources with highly concentrated ions, like hard rocks or underground deposits of salty water normally often often is often known as brines. Now now not handiest will those sources now now not be enough to fulfill demand, but mining them also comes with environmental consequences (SN: three/15/22).

Liu, though, has identified a material that might perchance make extraction which that it's possible you are going to in point of fact well imagine from untapped sources. She’s eyeing brines left over from geothermal and desalination processes, wastewater from fracking and even seawater, that may per chance one day provide an unlimited supply of lithium — if it truly is miles ready to be tapped. A significant challenge, though, is that seawater has a sodium-to-lithium ratio of roughly 20,000-to-1, nowhere near the present sources which have ratios inside of the diversity of hundreds-to-1.

Pulling lithium ions from low-concentration solutions for commercial use would require so much more research, Liu says. But her efforts have made huge strides toward more efficient extraction of resources, says University of Chicago molecular engineer Matthew Tirrell, who brought Liu on as an assistant professor in 2018. And it’s now now not only lithium extraction: “Her work is setting the stage for other processes that involve ions moving in porous, confined spaces,” he says, with future applications starting from finding the way you are going to speed up chemical reactions to potentially treating patients with mercury or lead poisoning.

Selecting for lithium

The method that Liu is working with — normally often often is often known as electrochemical intercalation — has handiest recently been used for extracting resources. First, the researchers dunk a material filled with ion-sized passageways into briny water. The lithium ions inside of the water enter the fabric’s lattice of channels and will per chance be captured there. But briny water also contains sodium ions, among others, which push their way into those channels, cutting back the quantity of lithium that will per chance be taken up.

Liu started attempting to locate a wonderful dunking material around 2016 at some point of her postdoctoral work at Stanford University. She knew it became important to get it right: “This material’s property will determine how tons selectivity [for lithium] we are ready to get, and what source water we are ready to use,” Liu says. The more practical the selectivity, the more lithium captured. So she scoured the scientific literature for a material that fit the bill. It needed to be stable in water and pay attention to its structure even when stuffed with ions.

She in some way settled on iron phosphate. The oxygen inside of the iron phosphate bonds more easily with lithium than with the competing sodium ions. The larger sodium ions could make bigger the channels, but the lithium-oxygen bonds keep the channels small and receptive to more lithium. Once the fabric is stuffed with ions, it truly is miles moved to freshwater where the researchers apply electric currents to expel the ions. Then they add a hydroxide, which mixes with the lithium to form solid lithium hydroxide, the raw material utilized in EV batteries.

The amount of lithium that iron phosphate can currently extract is “spectacular,” says physicist Steven Chu of Stanford University. Chu, former U.S. Secretary of Energy, worked with Liu at some point of her postdoctoral research. “Having done that, which that you're going to provide the option to rest for your laurels and say, ‘That’s great.’ But she’s also driven [to ask], ‘Is it going to be practical?’”

In her lab in Chicago, Liu has been striving to make the fabric more efficient. Her team studies how the lithium and sodium ions enter the fabric’s holes, in what order and how they engage inside of the fabric. By better working out the ions’ behavior, Liu says, the team can toughen the fabric’s performance.

Mining for working out

Liu’s team could be developing a new method for separating rare earth elements, which she says is “in truth more not easy” than lithium extraction. These 17 elements are essential for contemporary technologies, including wind turbines and smartphones (SN: 1/sixteen/23). But often found together, they has to be separated — a not easy task as a consequence of their similar size and chemistry.

Besides these two methods, tons of the lab’s work makes a speciality of basic materials science. “We just accumulate progressively more knowledge, so then we are ready to initiate to predict things,” she says. That’s how she landed on iron phosphate: After many of research, it became the primary material that the team tried.

It’s this deep working out that makes Liu stand out, Chu says. There may per chance be “a small variety of people it's possible you are going to in point of fact have got to definitely should understand of” because they often come up with clever, new approaches, he says, “and she’s one among them.”

Liu didn’t always dream of being a materials scientist, and even a professor. But at some point of her Ph.D. at Stanford, she realized that she loved the research environment. “I in truth experience solving the puzzle,” she says. “That made me come to a decision that more than likely I desire to are trying this job for a lifetime. It’s fun.”

On the weekends, she has fun of a distinct sort: playing Legos or riding bikes together with her kids. She’s started to show her son about the solar system and photosynthesis. “We are attempting to see whether we just can keep the fun,” she says, “but sneak in a little of little bit of the science.”