Global lithium production has more than tripled in the last decade. Current methods of extracting lithium from rock ores or brines are slow and come with high energy demands and environmental costs. They also require sources of lithium which are incredibly concentrated to begin with and are only found in a few countries.

Now, researchers at the University of Chicago Pritzker School of Molecular Engineering (PME) have optimized a new method for extracting lithium from more dilute—and widespread—sources of the mineral, including seawater, groundwater, and “flowback water” left behind from fracking and offshore oil drilling.

The work is published as an open access paper in Nature Communications.

Right now there is a gap between the demand for lithium and the production. Our method allows the efficient extraction of the mineral from very dilute liquids, which can greatly broaden the potential sources of lithium.

—Chong Liu, Neubauer Family Assistant Professor of Molecular Engineering and senior author

In the new research, Liu and her colleagues showed how certain particles of iron phosphate can most efficiently pull lithium out of dilute liquids. Their new findings could hasten an era of faster, greener lithium extraction.

Liu’s team’s general approach isolates lithium based on its electrochemical properties, using crystal lattices of olivine iron phosphate. Because of its size, charge and reactivity, lithium is drawn into the spaces in the olivine iron phosphate columns—like water being soaked into the holes in a sponge. But, if the column is designed perfectly, sodium ions, also present in briny liquids, are left out or enter the iron phosphate at a much lower level.

In the new work, Liu and her colleagues, including first author of the new paper Gangbin Yan, a PME graduate student, tested how variation in olivine iron phosphate particles impacted their ability to selectively isolate lithium over sodium.

When you produce iron phosphate, you can get particles that are drastically different sizes and shapes. In order to figure out the best synthesis method, we need to know which of those particles are most efficient at selecting lithium over sodium.

—Gangbin Yan

The research team synthesized olivine iron phosphate particles using different methods, resulting in a range of particle sizes spanning 20 to 6,000 nanometers. Then, they divided those particles into groups based on their size and used them to build electrodes that could extract lithium from a weak solution.

When iron phosphate particles were too large or too small, the researchers discovered, the particles tended to let more sodium into their structures. That led to less pure extractions of lithium.

It turned out that there was this sweet spot in the middle where both the kinetics and the thermodynamics favor lithium over sodium. We have to keep this desired particle size in mind as we pick synthesis methods to scale up. But if we can do this, we think we can develop a method that reduces the environmental impact of lithium production and secures the lithium supply in this country.

—Chong Liu

This work was supported by the National Science Foundation and the Department of Energy Office of Science.

Resources

• Yan, G., Wei, J., Apodaca, E. et al. Identifying critical features of iron phosphate particle for lithium preference. Nat Commun 15, 4859 (2024). doi: 10.1038/s41467-024-49191-3