New acid process could make lithium extraction cheaper and safer

A team of researchers at MIT and a startup company called Rock Zero have invented a new way to pull lithium from rock. The method uses a weak acid called ammonium fluoride to dissolve the mineral spodumene, which contains lithium. According to Yet-Ming Chiang, an MIT professor and one of the study authors, "At scale, we believe this will be the lowest-cost way of sourcing lithium in the world." Chiang is also the founder of climate tech companies Form Energy and Addis Energy.

Lithium is essential for making batteries in electric cars and storing renewable energy. Today, mining companies get lithium in two main ways. The first is brine extraction, where salty water containing dissolved lithium is pumped up and left in enormous evaporation pools to concentrate the metal. This method works only in certain parts of the world and uses huge amounts of land. The second way is hard-rock mining, which involves blasting ore, heating it to extreme temperatures, and treating it with dangerous chemicals.

The new process works differently. When ammonium fluoride dissolves silicate minerals, it releases not just lithium but also alumina and silica—materials that have their own commercial value. Current lithium mining from hard rock requires roasting ore in a kiln at very high temperatures to make the lithium accessible. This step is energy-intensive and produces carbon emissions. The new method avoids this entirely, working at temperatures around 95 degrees Celsius (200 degrees Fahrenheit) in simple plastic tanks.

The idea grew out of research at Sublime Systems, another company founded by Chiang, which makes cement using electricity instead of traditional fuel. Researchers there needed to find a reactive form of silica to create stronger cement. Dissolving silicate minerals is possible but usually requires hydrofluoric acid, an extremely hazardous chemical. Some other fluorine-based acids produce hydrofluoric acid as a dangerous side effect during reactions.

Chiang's breakthrough came from an unexpected source. "I was remodeling a shower in Framingham, Massachusetts, about 25 years ago," he says. "So when we started this project, I remembered that glass etching cream and thought, 'What's in that?'" Glass etching cream, sold at craft stores, contains ammonium fluoride. Lab tests showed this weak acid could dissolve silicate minerals without creating hazardous hydrofluoric acid as a byproduct.

In experiments, the new process extracted nearly all the lithium from spodumene ore within a couple of days. The team later improved the method to complete extraction in under 12 hours, according to Benjamin Mowbray, the study's first author and CTO of Rock Zero. The process produces three useful products: lithium carbonate for batteries, alumina for making aluminum, and silica for concrete. The ammonium fluoride acid is recycled and reused in the same loop.

Chiang describes this as "nose-to-tail" mining, using every part of the ore with no waste. Laboratory tanks in Cambridge, Massachusetts currently handle three kilograms of spodumene concentrate per batch. The researchers have calculated that once fully scaled, the process could extract lithium for less than $6,000 per metric ton. This projected cost is lower than other hard-rock lithium extraction methods today and could compete with brine extraction.

Rock Zero has designed a pilot plant and is searching for a location to build it. The company aims to complete construction by the end of 2026 and begin operating by 2027. Conversations are underway with mining industry partners about potential collaboration.

However, the company faces real challenges. Lithium prices have swung wildly—climbing to a peak in 2022, dropping to lows in late 2024, and slowly rising since early 2026. Simon Jowitt, chair of exploration geology at the University of Nevada, Reno, notes that "People are waiting to see what happens with the lithium price. It's a crowded market, and there's some big players out there." The global lithium market is still relatively small, which makes it prone to price swings.

New companies entering lithium mining must compete against established giants that already control large operations. Alternative battery technologies, such as sodium-ion batteries that do not require lithium, could also reshape the market. Jowitt also believes some of Rock Zero's cost projections may be too optimistic. Despite these obstacles, Rock Zero's team plans to apply the technology not only to lithium but eventually to other minerals extracted from silicate rocks, which make up much of Earth's crust.