MIT researchers develop new low-cost lithium extraction method

A research team has found a new method to extract lithium from rock, potentially reducing battery costs if the supply becomes limited. Published in Science, the study focuses on lowering energy consumption and waste during lithium extraction from hard rock ore.

Currently, lithium-ion batteries dominate the market thanks to their scale, and the global supply chain is well-developed and efficient, making alternatives less competitive on price. However, this advantage relies heavily on affordable lithium mainly sourced from South American brine deposits. Although lithium is plentiful, easy-to-access and inexpensive deposits are scarce.

This reality has kept spodumene, a lithium-rich mineral found in hard rock, in the spotlight. It is the most common lithium ore worldwide, but processing it remains costly. The conventional method involves heating the ore to around 1,000°C and treating it with sulfuric acid to extract the lithium, a process that consumes significant energy and produces sulfur waste.

Researchers at MIT and their partners have developed an alternative process. Instead of high-temperature roasting, they use an ammonium fluoride solution heated to about 70°C to break down the mineral. This chemical reaction successfully separates the ore into streams of lithium, silicon, and aluminum.

In this process, lithium forms a solution as lithium fluoride, while silicon and aluminum follow different pathways: silicon forms a soluble compound, and aluminum forms a solid intermediate. Each element is then processed separately.

Aluminum extraction consumes the most energy, requiring staged heating to 300°C and then to 700°C to produce high-purity aluminum oxide. This step occurs after the initial separation rather than at the beginning of the cycle.

The silicon component is much simpler to process. Adding ammonia converts the silicon into silicon dioxide, which precipitates out and can be used in concrete, helping to offset overall processing costs.

Lithium remains as lithium fluoride in the solution, which is usable directly for making lithium battery electrolytes. Alternatively, it can be converted into lithium nitrate and lithium oxide, both of which are common in battery manufacturing.

A notable feature of the breakthrough is the process’s chemistry management. Ammonia and hydrogen fluoride generated during the reactions are recycled to recreate ammonium fluoride, reducing waste and material loss, though the hydrogen fluoride still requires careful handling.

Economically, the method looks promising. Conventional spodumene extraction costs about $9,000 per tonne of lithium, but this new process could reduce that figure to just over $5,000 per tonne, making it comparable to high-quality brine extraction. Additional revenue generated from byproducts might lower costs even further.

However, some uncertainties remain. Real-world costs will still depend on ore quality, market prices, and infrastructure investments. Nonetheless, this work offers a fresh perspective on lithium sourcing, focusing on how the mineral is extracted rather than just where it comes from.