Gathering lithium, a crucial element in batteries for smartphones, electric cars and the electrical grid, is a time-consuming and energy-intensive process, but new technology could make it much easier.
Researchers at The University of Texas at Austin developed a new way to separate lithium from other co-occurring elements, potentially speeding up extraction of this critical element and increasing domestic supply. They developed nanoscale, artificial channels, inspired by the natural doors that let ions and molecules in and out of living cells, that allow lithium to pass through while restricting other competing ions that typically come with it.
These channels, tiny pores that sit inside membranes, were two to five times more selective for lithium compared with other recently developed lithium transporters. The researchers say their channels are among the most selective ever created.
"Lithium is in our phones, our cars and the power grid, but getting it out of the ground cleanly is still a hard problem," said Manish Kumar, a professor in the Fariborz Maseeh Department of Civil, Architectural and Environmental Engineering and the McKetta Department of Chemical Engineering who is one of the leaders of the new research published in the Journal of the American Chemical Society . "Our goal is a process that is faster, cleaner and easier to run."
Lithium is found in underground salty water called brine, in hard rock and in recycled batteries. It mixes with other dissolved substances, including sodium, potassium, magnesium, and calcium.
Separating lithium from these look-alikes is difficult. Current methods are time consuming, energy intensive and can leave behind harmful waste products.
This research builds on technology previously developed to separate out other rare earth elements used for wind-turbine magnets, electric-vehicle batteries and display screens. The new study extends this approach to lithium, demonstrating how interactions between ions and chemical groups at the channel entrance, together with the channel's confined structure, can enable highly selective lithium transport.
"We now have a toolkit rather than a one-off result," said Harekrushna Behera, a research scientist in Kumar's lab. "By understanding how ions interact with the chemical groups at the channel entrance, we can work toward designing more selective channels for lithium and potentially other critical minerals."
The team is now working to pack these channels into larger membranes, using a membrane material they recently developed from interconnected, cell-like layers that can be made from lipids or plastic-like polymers. The goal is a continuous process that separates lithium without the need for harsh solvents.
Experiments with real brines, which contain many salts at once, and at industrial scale will be needed to learn how the approach performs outside the lab. The researchers also see potential uses beyond mining, including recycling lithium from used batteries and, eventually, building better separators inside the batteries themselves.
Other team members on the project include professor Venkat Ganesan, Tyler J Duncan, Hyeonji Oh, Chenhao Yao, Raman Dhiman and Siqi Wang of the McKetta Department of Chemical Engineering; Laxmicharan Samineni of chemical engineering and the Fariborz Maseeh Department of Civil, Architectural and Environmental Engineering and Luke Hatch of the College of Natural Sciences' Department of Chemistry.
