Pictured: Black mass powder from recycled lithium ion ev batteries.
As the race to secure supplies of lithium accelerates, University of South Carolina Molinaroli College of Engineering and Computing researchers are pursuing an unlikely solution: technology originally designed to make drinking water cleaner.
The timing is significant. Demand for lithium is rising rapidly as electric vehicles, consumer electronics and energy storage systems become more widespread. Recovering the critical mineral from alternative sources such as brines, seawater and spent batteries could help strengthen domestic supply chains, reduce dependence on conventional mining and lower environmental impacts.
Chemical Engineering Professor Zhenmeng Peng is helping address the challenge by adapting a technology his laboratory originally developed to improve drinking water.
“We started this research about six years ago, and at that time, our objective was to desalinate and purify water,” Peng says. “As we better understood the capabilities of the technology, we realized that the same platform could solve a much broader range of separation challenges.”
At the center of Peng's research is a technology called redox-mediated electrodialysis. The basic idea of the platform is straightforward: the system uses electricity and specially designed membranes to separate dissolved materials from water. By carefully controlling how charged particles move, the technology can clean water and be used in other applications ranging from lithium recovery, battery recycling and fuel cell technologies.
One of Peng’s ongoing projects uses the platform to remove per- and polyfluoroalkyl substances (PFAS), often called “forever chemicals,” from drinking water and other contaminated sources. The same underlying principles can also be used to recover valuable materials from lithium-containing solutions.
According to Lithium Harvest, global demand for lithium increased by nearly 30% in 2024 and is expected to grow substantially by 2030 as adoption of electric vehicles and renewable energy technologies continues to accelerate.
The goal is to produce high-purity lithium salts from brines and to recover lithium from spent batteries so these valuable materials can be reused.
- Zhenmeng Peng
Meeting that demand isn’t simply a matter of finding more lithium. Most of the world’s lithium reserves are found in brines—highly concentrated saltwater solutions that contain lithium along with large amounts of sodium, magnesium, calcium, potassium and other dissolved minerals. Recovering lithium from these elements is one of the biggest challenges in producing high-purity lithium.
Peng’s platform addresses this challenge by applying an electric field across ion-exchange membranes. Under the electric field, positively and negatively charged ions migrate in opposite directions. Carefully designed cation (positive)-and-anion (negative)-exchange membranes guide this ion transport, allowing salts to be removed while concentrating them in a separate stream.
“When an electric field is applied, ions migrate according to their charge,” Peng says. “By incorporating ion-exchange membranes, we direct that movement into separate flow channels. The result is that the feed water is purified while the dissolved ions are concentrated into a second stream for further processing.”
Unlike conventional electrodialysis, Peng’s system incorporates reversible redox reactions that help move ions more efficiently through the system while reducing energy use. The technology relies on many of the same principles found in batteries and fuel cells.
“The same electrochemical concepts underpin batteries, fuel cells and our separation technology,” Peng says. “By controlling electron transfer and ion transport, we can tailor the platform for different applications – from producing clean water to recovering critical materials.”
For lithium recovery, one of the biggest hurdles is selectivity. While lithium may be present in a solution, it is often mixed with larger concentrations of other dissolved salts. Peng’s team is developing specialized membranes that allow lithium ions to pass through while blocking competing ions.
“It’s important to develop a selective membrane that only allows the lithium ions to go across it to recover lithium salts, while all the other ions are rejected,” he says. “That enables us to recover high-purity lithium salts from seawater, natural brines and other complex feed streams.”
Although the technology began as a way to improve water treatment, Peng sees significant potential in recovering critical materials. In addition to lithium, the same approach could help recover nickel, cobalt, and other valuable metals needed for battery manufacturing, energy infrastructure and advanced technologies essential to economic growth and national security.
Peng is now expanding collaborations with researchers at Savannah River National Laboratory and advancing lithium recovery efforts through the college’s Carolina Institute for Battery Innovation.
“Each application has its own motivation,” Peng says. “For water treatment, our goal is to produce clean water. For lithium recovery, the goal is to produce high-purity lithium salts from brines and to recover lithium from spent batteries so these valuable materials can be reused.”