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Lithium recovery: A critical challenge for battery tech

ORNL Corporate Fellow Parans Paranthaman. Image credit: Carlos Jones, ORNL

DOE’s National Blueprint for Lithium Batteries 2021–2030 makes it clear that lithium production is a national priority. The report notes that the worldwide lithium battery market is expected to grow by a factor of 5 to 10 in the next decade and warns: “The U.S. industrial base must be positioned to respond to this vast increase in market demand that otherwise will likely benefit well-resourced and supported competitors in Asia and Europe.”

Taking advantage of this impending increase in demand for lithium will be particularly challenging for the United States, which currently produces very little of the critically important mineral.

“Less than 2 percent of our lithium comes from the U.S. and Canada,” said ORNL Corporate Fellow Parans Paranthaman, who has spent years investigating alternative sources of lithium. “Forty percent comes from Australia. We get about 35 percent from South America — Argentina, Bolivia, Chile — and the rest comes from China.

“Because we are using more lithium batteries in electric cars and many other devices, to alleviate supply chain shortages we have identified alternative sources of lithium. The most promising of these is recovering lithium from brine generated by geothermal power plants or from mine tailings.”

Mineral-rich brine

Geothermal plants generate power by drilling into reservoirs of pressurized, superheated water deep underground and pumping it to the surface. Depressurized, the water turns to steam and spins turbines that power generators to produce electricity. The leftover, mineral-laden water, known as brine, contains high concentrations of several minerals and a much lower concentration of lithium.

“We see 300 to 400 parts per million of lithium chloride,” Paranthaman said. “Compare that to 50,000 parts per million of sodium chloride. In the brine, we have sodium chloride, potassium chloride, calcium chloride and manganese at very high concentrations, whereas the concentration of lithium is low. So the challenge is to extract the lithium efficiently and with a high level of purity.

Though the concentration of lithium is relatively low in geothermal brines compared to other sources, brines require no mining, and no wells have to be drilled because they are already being exploited for power production.

Normally, geothermal power plants pump their cooled brine back underground. However, Paranthaman is working with scientists at ORNL, DOE’s Critical Materials Institute and industry partner All-American Lithium to devise methods of first recovering the lithium from the brine. The key to this recovery is the development of a sorbent material that will selectively adsorb, or chemically remove, lithium chloride from the brine. So far, the material that has shown the most promise is pure or iron-doped lithium-aluminum-layered double hydroxide chloride, or LDH.

“We designed the sorbent to exclusively adsorb lithium chloride,” Paranthaman said. “LDH has the advantage of being relatively low cost and highly selective for lithium — meaning that it not only adsorbs a large percentage of the available lithium, but it doesn’t recover other minerals in the process.”

In tests, simulated brine was pumped through a column containing layers of LDH separated by water molecules and hydroxide ions that preferentially admit lithium chloride ions and block sodium and potassium ions. This process removed more than 90 percent of the lithium from the simulated brine.

Paranthaman and his colleagues are also investigating using a membrane that will concentrate the lithium chloride solution before it is exposed to the sorbent. This is expected to increase the efficiency of the process. “Using the membrane, we can go from roughly a 3-percent lithium chloride solution to a 22-percent solution. We hope to be able to go all the way to 40 percent. When we concentrate the lithium chloride, the sodium chloride and potassium chloride — which have lower solubility — precipitate out, so they can be removed by filtering. This results in a pure lithium chloride solution that can then be converted to lithium hydroxide or lithium carbonate. These are the starting materials for lithium battery production.”

A good situation to be in

If this technology can be scaled up and employed on an industrial level, it is estimated that a 50-megawatt geothermal plant could recover 15,000 tons of lithium carbonate per year, and there are more than 20 geothermal power plants just in the vicinity of California’s Salton Sea. Currently, the entire world’s production of lithium carbonate is only around 160,000 tons. So, if the lithium recovery capacity of these geothermal plants were to be fully utilized, it would provide more than enough lithium to meet domestic demands.

“Then, we could be an exporter of lithium carbonate,” Paranthaman said. “That would be a good situation to be in.”

Critical leftovers

Paranthaman and his colleagues are also teaming up with the Critical Materials Institute as well as several small companies and university partners to develop conceptually similar methods for recovering lithium from mine tailings left over from boron mining operations.

“As part of CMI’s Critical Materials Project, we are working with Rio Tinto Borates, among others, which has been mining boron in California for almost 150 years,” Paranthaman said. “Boron tailings contain lithium sulfate. So we’re in the process of developing a prepilot demonstration of lithium recovery from these tailings right now. We expect that we will be ready for a full-scale demonstration within a year.”

Recovering lithium from mine tailings, naturally, uses different methods and processes than recovering lithium from geothermal brine.

“Chemistry-wise, geothermal recovery is a chloride stream; mine tailings are a sulfate stream, so they require different processes,” Paranthaman said. “However, the idea is the same, and the product resulting from both processes will be the same.”

Taking it to the next level

Over the longer term, Paranthaman and his colleagues envision mounting a comprehensive effort to address the challenges associated with lithium-ion batteries. For example, in addition to lithium, there is a critical need for nickel, cobalt and graphite in the production of lithium-ion batteries.