Device extracts lithium from Dead Sea brine

Sustainable ways to obtain lithium are necessary to make batteries for an increasingly electrified world. An efficient new electrochemical device that could extract the critical metal from thousands of liters of seawater at a time offers a way forward (Science 2024, DOI: 10.1126/science.adg8487).

The device, which relies on a cheap electrode material used in today’s lithium-ion batteries, can extract over 84% of lithium from natural or simulated Dead Sea water. Although the Dead Sea is thought of as the epitome of saltiness, its waters contain lithium salts at 40 parts per million (ppm)—relatively low compared to the hundreds of parts per million in brines mined today. “We are trying to extract lithium from unconventional resources to solve lithium supply issues,” says Zhiping Lai, a chemical engineer at King Abdullah University of Science and Technology (KAUST).

Lithium is mined mostly from concentrated brines or hard-rock ores. The former involves environmentally damaging evaporative ponds that threaten local wildlife and the water supplies of surrounding rural communities, and the latter is energy intensive. Companies are developing chemical or physical processes to directly extract lithium from dilute salt waters, such as the wastewater produced during drilling for geothermal energy or oil. But these direct lithium extraction (DLE) techniques rely on expensive sorbents that need to be regenerated using heat or harsh chemicals.

Lai, Kuo-Wei Huang, and colleagues made a two-chamber DLE device that uses minimal electricity, which could come from renewable sources. The cathode chamber holds brine containing lithium concentrations of 5–80 ppm and tens of thousands of parts per million of magnesium, sodium, and calcium. The anode chamber contains a conductive salty solution that collects lithium ions.

Each compartment has a pair of electrodes made of silver and lithium iron phosphate (LFP). LFP has a layered structure that easily takes up and releases lithium while keeping out other ions. Under a small electric field, the LFP electrode in the cathode chamber selectively takes up lithium ions from the brine, while the LFP at the anode sheds lithium ions into the collection solution.

When all the lithium from the brine is extracted, the researchers switch the electrodes and replace the brine, and the process continues. After a few cycles, the team adds sodium carbonate to the extraction solution, which produces 99.95% pure, battery-grade lithium carbonate powder that can be filtered out.

As a demonstration, the team constructed a pilot-scale system with 1,000 L tanks and 300 electrode pairs with a total area of about 34 m². From more than 9 metric tons of artificial seawater that contained 65 ppm of lithium ions and hundreds of times as much calcium and magnesium, the automated setup extracted over 84% of lithium. “The yield would improve further with higher concentration,” Lai says.

Seth B. Darling, an advanced materials and energy specialist at Argonne National Laboratory, finds the work creative in its repurposing of battery electrode materials to increase lithium supplies for batteries. The silver electrode and solvent materials are expensive and would need to be replaced by cheaper ones, he says. But the method’s ability to extract lithium from lower-concentration brines is “particularly exciting. As global demand for lithium increases, this technique has the potential to support sustainable and efficient extraction processes.”