The future of lithium is electrifying. Cars and trucks powered by lithium batteries rather than fossil fuels are, to many people, the future of transportation. Rechargeable lithium batteries are also crucial for storing energy produced by solar and wind power, clean energy sources that are a beacon of hope for a world worried about the rapidly changing global climate.
Prospecting for new sources of lithium is booming, fueled by expectations that demand for lightweight, rechargeable lithium batteries — to power electric vehicles, cell phones, laptops and renewable energy storage facilities — is about to skyrocket.
Even before electric cars, lithium was a hot commodity, mined for decades for reasons that had nothing to do with batteries. Thanks to lithium’s physical properties, it is bizarrely useful, popping up in all sorts of products, from shock-resistant glass to medications. In 2018, those products accounted for nearly half of the global lithium demand, according to analyses by the Frankfurt-based Deutsche Bank. Batteries for consumer electronics, such as cell phones or laptops, accounted for another 25 percent or so of the demand. Electric vehicles accounted for most of the rest.
That breakdown will soon be turned on its head: By 2025, as much as half of the demand for lithium will be from the electric vehicle industry, some projections suggest. Global demand for the metal is expected to rise at least 300 percent in the next 10 to 15 years, in large part because sales of electric vehicles are expected to increase dramatically. Right now, there are about 2 million electric vehicles on the road worldwide; by 2030, that number is projected to grow to over 24 million, according to the industry research firm Bloomberg New Energy Finance. Electric vehicle giant Tesla has been on a worldwide quest for lithium, inking deals to obtain lithium supplies from mining operations in the United States, Mexico, Canada and Australia.
As a result, lithium prices in global markets have been on a roller coaster in the last few years, with a sharp spike in 2018 due to fears that there just might not be enough of the metal to go around. But those doomsday scenarios are probably a bit overwrought, says geologist Lisa Stillings of the U.S. Geological Survey in Reno, Nev. Lithium makes up about 0.002 percent of Earth’s crust, but in geologic terms, it isn’t particularly rare, Stillings says. The key, she adds, is knowing where it is concentrated enough to mine economically.
To answer that question, researchers are studying how and where the forces of wind, water, heat and time combine to create rich deposits of the metal. Such places include the flat desert basins of the “lithium triangle” of Chile, Argentina and Bolivia; volcanic rocks called pegmatites in Australia, the United States and Canada; and lithium-bearing clays in the United States.
The hunt to find and extract this “white gold” is also spurring new basic geology, geochemistry and hydrology research. Stillings and other scientists are examining how clays and brines form, how lithium might move between the two deposits when both occur in the same basin and how lithium atoms tend to position themselves within the chemical structure of the clay.
Seeking simpler sources
Lithium, in its elemental form, is soft and silvery and light, with a density about half that of water. It’s the lightest metal on the periodic table. The element was discovered in 1817 by Swedish chemist Johan August Arfwedson, who was analyzing a grayish mineral called petalite. Arfwedson identified aluminum, silicon and oxygen in the mineral, which together made up 96 percent of the mineral’s mass.
The rest of the petalite, he determined, was made up of some sort of element that had chemical properties similar to potassium and sodium. All three elements are highly reactive with other charged particles, or ions, to form salts, are solid but soft at room temperature, have low melting points and tend to dissolve readily in water. Thanks to their similarities, these elements, along with rubidium, cesium and francium, were later grouped together as “alkali metals,” forming most of the periodic table’s Group 1 (SN: 1/19/19, p. 18). Lithium’s affinity for water helps explain how it moves through Earth’s crust and how it can become concentrated enough to mine.
The basic recipe for any kind of lithium-rich deposit includes volcanic rocks plus a lot of water and heat, mixed well by active tectonics. Worldwide, there are three main sources of lithium: pegmatites, brines and clays.
Most pegmatites are a type of granite formed out of molten magma. What makes pegmatites interesting is that they tend to contain a lot of incompatible elements, which resist forming solid crystals for as long as possible. The rocks form as the magma beneath a volcano cools very slowly. The magma’s chemical composition evolves over time. As elements drop out of the liquid to form solid crystals, other elements, like lithium, tend to linger in the liquid, becoming more and more concentrated. But eventually, even that magma cools and crystallizes, and the incompatibles are locked into the pegmatite.
Before the 1990s, pegmatites in the United States were the primary source of mined lithium. But extracting lithium ore, primarily a mineral called spodumene, from the rock is costly. On top of the cost of actual mining, the rock has to be crushed and treated with acid and heat to extract the lithium in a commercially useful form.
In the 1990s, a much cheaper source of lithium became an option. Just beneath the arid salt flats spanning large swaths of Chile, Argentina and Bolivia circulates salty, lithium-enriched groundwater. Miners pump the salty water to the surface, sequestering it into ponds and letting it evaporate in the sun. “Mother Nature does most of the work, so it’s really cheap,” Stillings says.
What’s left behind after the evaporation is a sludgy, yellowish brine. To extract battery-grade lithium in commercially useful forms, particularly lithium carbonate and lithium hydroxide, the miners add different minerals to the brine, such as sodium carbonate and calcium hydroxide. Reactions with those minerals cause different types of salts to precipitate out of the solution, ultimately producing lithium minerals.
Compared with pegmatite extraction, the process for extracting lithium from the brine is extremely cheap; as a result, brine mining currently dominates the lithium market. But in the hunt for more lithium, the next generation of prospectors are looking to a third type of deposit: clay.
Clays are the hardened remnants of ancient mud, produced by the slow settling of tiny grains of sediment, such as within a lake bed. To get lithium-enriched clay requires the right starting ingredients, particularly lithium-bearing rocks such as pegmatite and circulating groundwater. The groundwater leaches the lithium from the rocks and transports it to a lake where it becomes concentrated in the sediments.
The western United States, it turns out, has all the right ingredients to make lithium-rich clay. In fact, in 2017 in Nature Communications, researchers suggested that some ancient supervolcano craters that became lakes, such as the Yellowstone caldera, would be excellent sources of lithium.
Beneath North America lies a shallow pool of magma that feeds the Yellowstone supervolcano. For the last 2 million years or so, Yellowstone volcanism has been located in northwestern Wyoming (and is the centerpiece of Yellowstone National Park). But the Yellowstone hot spot isn’t stationary. Over the last 16 million years, as the North American plate has slowly slid to the southwest, it has moved over the stationary, shallow magma body, leaving a pockmarked track of volcanic craters stretching from Nevada to Yellowstone. One of the oldest known Yellowstone craters, called McDermitt Caldera, filled with water, then later dried up, leaving behind a potential treasure trove of lithium-rich clay. Vancouver-based Lithium Americas Corp., which plans to begin mining operations at a site called Thacker Pass within the caldera in 2022, estimates that by 2025, the lake bed could provide as much as 25 percent of the world’s lithium.
In the United States, Stillings says, McDermitt is “one of the very large resources that we know exists.” But lithium clays have some hurdles to clear before they can compete with brines. Retrieving the lithium ore requires open-pit mining, which is more expensive than pumping up the brine. And processing the clay to extract lithium carbonate or other industry-ready minerals is also pricey. Lithium Americas and other companies that claim to have developed their own clean, inexpensive extraction processes haven’t yet demonstrated that they will be competitive with brine mining.
