The surge in the electric vehicle market has led to a massive increase in the demand for lithium, a key mineral used in lithium-ion batteries. Over the past decade, global lithium production has more than tripled. However, the current methods of extracting lithium from rock ores or brines are not only slow but also entail high energy demands and significant environmental costs. Moreover, these methods rely on sources of lithium that are highly concentrated and found only in a few countries.
Now, researchers at the University of Chicago Pritzker School of Molecular Engineering (PME) have successfully developed an innovative method for extracting lithium from more diluted and widely available sources of the mineral. These sources include seawater, groundwater, and “flowback water” left behind from fracking and offshore oil drilling.
“Right now, there is a gap between the demand for lithium and the production,” said Chong Liu, senior author of the new work. “Our method allows the efficient extraction of the mineral from very dilute liquids, which can greatly broaden the potential sources of lithium.”
Liu and her colleagues have uncovered a groundbreaking method using iron phosphate particles to efficiently extract lithium from dilute liquids. This discovery has the potential to revolutionize lithium extraction, making it faster and more environmentally friendly.
Currently, the predominant methods involve either mining lithium rock ores, which requires heavy machinery and acid treatment, or extracting lithium from brine pools using large amounts of water over a period of more than a year.
“These methods aren’t particularly environmentally friendly to begin with, and if you start trying to work with less concentrated sources of lithium, they’re going to become even less efficient,” said Liu. “If you have a brine that is 10 times more dilute, you need 10 times more briny water to get the same amount of lithium.”
The team’s approach isolates lithium based on its electrochemical properties, utilizing crystal lattices of olivine iron phosphate. Due to its size, charge, and reactivity, lithium is attracted into the spaces in the olivine iron phosphate columns, akin to water being absorbed into a sponge. By designing the column perfectly, sodium ions, also present in briny liquids, are excluded or enter the iron phosphate at significantly lower levels.
In their latest research, Liu and her colleagues explored how variations in olivine iron phosphate particles influenced their capacity to selectively isolate lithium over sodium.
“When you produce iron phosphate, you can get particles that are drastically different sizes and shapes,” explains Gangbin Yan, a PME graduate student and the first author of the new paper. “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.”
Using various methods, the research team successfully created olivine iron phosphate particles of varying sizes, from 20 to 6,000 nanometers. These particles were then grouped based on size and used to construct electrodes capable of extracting lithium from a dilute solution.
The team found that when the iron phosphate particles were too small or too large, they allowed more sodium into their structures, resulting in less pure lithium extraction.
“It turned out that there was this sweet spot in the middle where both the kinetics and the thermodynamics favor lithium over sodium,” said Liu.
The findings are crucial for advancing electrochemical lithium extraction for commercial use. They indicate that researchers should not only focus on producing olivine iron phosphate but also on producing it at the optimal particle size.
“We have to keep this desired particle size in mind as we pick synthesis methods to scale up,” Liu said. “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.”
Journal reference:
- Gangbin Yan, Jialiang Wei, Emory Apodaca, Suin Choi, Peter J. Eng, Joanne E. Stubbs, Yu Han, Siqi Zou, Mrinal K. Bera, Ronghui Wu, Evguenia Karapetrova, Hua Zhou, Wei Chen & Chong Liu. Identifying critical features of iron phosphate particle for lithium preference. Nature Communications, 2024; DOI: 10.1038/s41467-024-49191-3
