How does lithium extraction actually work?

Lithium does not occur in the Earth's crust in its elemental form, but only as a compound. Complex processes are required to extract it. These differ fundamentally depending on whether lithium salts dissolved in water (brine) or lithium-containing minerals are involved. The first part of this article describes the most significant method in terms of quantity: extraction from minerals, primarily spodumene.

Written by Dr. Ulla Reutner

Four white-beige ore chunks lie on the palm of a hand — Spodumene pegmatite ore is the most important source for the production of lithium hydroxide, which is used in lithium-ion batteries.

Part 1: Extraction from hard rock

Over the past two decades, global lithium production has increased more than tenfold, from approximately 20,000 tonnes in 2005 to 240,000 tonnes in 2024. This increase was driven in particular by the sharp rise in demand for lithium-ion batteries. Around 75 per cent of the amount produced to date is used in this application. Demand will continue to rise significantly in the coming years. This provides an incentive to optimise manufacturing processes.

Currently, the mining of lithium pegmatites such as spodumene and subsequent processing cover approximately 60 percent of global demand. Between 30 and 35 percent of global production is obtained through brine evaporation, mainly from salt lakes. Direct lithium extraction (DLE), the latest production process, still contributes relatively little to meeting demand, at around ten percent. The processes differ fundamentally, as do the respective investment requirements, energy consumption and water consumption.

Aerial view of an open pit mine with terraced rock layers — Spodumene is mined in hard rock mines such as Greenbushes in southwestern Western Australia. The ore is processed into spodumene concentrate.

Extraction from spodumene and other hard rocks

Extraction from silicate rock, mainly in Australia, Canada and China, is largely based on the mining of spodumene ore (LiAlSi₂O₆) with a lithium content of 3.5 to 3.9 percent. Other industrially important lithium ores are petalite (LiAlSi₄O₁₀) and lithium mica (lepidolite, K(Li,Al)₃(Al,Si,Rb)₄O₁₀(F,OH)₂) with a maximum of three percent lithium, as well as the rarer phosphate mineral amblygonite (LiAl[PO₄]F) with a lithium content of approx. 4.7 percent.

Purification and concentration to SC6

The ores extracted in open-cast or underground mines are processed into concentrates. To do this, the ore is first crushed to a particle size of ten to twelve mm and then ground in a ball mill. In combination with screens or hydrocyclones, a grinding fineness of 75 micrometres is achieved. Where necessary, valuable by-products such as tantalum or niobium are separated using magnets or gravity separation.

The crushed ore mass is mixed with water and fed as slurry to a flotation plant, where the fine-grained lithium ore is separated from other minerals. To do this, the surface polarity of spodumene is changed by adding flotation agents. Increasing the surface polarity causes air bubbles to adhere to the particles. This gives them buoyancy so that they float to the surface and can be removed (positive flotation). Reverse flotation is also possible: with flotation agents that increase the surface polarity of the other minerals. These are then removed at the surface, while the spodumene remains in the slurry.

The flotation process involves several stages: coarse flotation is followed by several cleaning and post-treatment flotation stages. After separating the so-called gangue, the concentrated slurry is first roughly dewatered in a thickening plant and then further dewatered in ceramic disc filters, high-pressure filters or decanter centrifuges until the so-called spodumene concentrate (SC6, a high-purity lithium ore with a lithium content of about 6 percent) is produced. The aim is to further increase the lithium content by means of sensor-based sorting, pure particle flotation and ion-selective separation technologies.

From spodumene concentrate SC6 to lithium hydroxide

There are several pyrometallurgical and hydrometallurgical processes for producing the lithium compounds from spodumene concentrate that are ultimately required for industrial applications, such as battery manufacturing.

Calcination and subsequent extraction

A proven production method is calcination followed by sulphuric acid digestion. In this process, the spodumene concentrate is converted from an α structure to a more reactive β structure by roasting at over 1000 °C, from which lithium can be more easily isolated. Subsequent digestion with concentrated sulphuric acid at 250 to 300 °C produces soluble lithium sulphate. β-spodumene can also react in melts with sodium or potassium sulphate at 700 °C, which also produces lithium sulphate. Finally, lithium carbonate is precipitated from the solution by adding soda. It is converted to lithium hydroxide by ion exchange or reaction with lime milk and soda.

Alternatively, β-spodumene can be broken down under pressure with sodium or potassium hydroxide. This causes lithium hydroxide to dissolve. If, on the other hand, it is treated with sodium carbonate (soda) (process developed by Metso), soluble lithium sodium aluminosilicate is formed, from which the lithium is dissolved. It is precipitated as lithium hydroxide using lime milk.

An open rectangular container in an industrial environment contains a foamy grey liquid — Flotation is an important step in the concentration of lithium-bearing ore.

Digital 3D model of a multi-storey process plant with reactors, tanks, piping and other technical equipment — Metso produces battery-grade lithium hydroxide using its environmentally friendly alkaline pressure leaching process.

Prime Lithium is currently developing another optimised soda leaching process. In this process, β-spodumene mixed with soda is broken down at temperatures of up to 1000 °C. This produces lithium carbonate, which is washed out with water. The separated lithium carbonate is reacted with calcium hydroxide (causticising). Calcium carbonate precipitates, while lithium hydroxide remains in solution. Finally, lithium hydroxide monohydrate (LiOH·H₂O) is obtained by evaporation and crystallisation.

In a process developed by Tesla, β-spodumene is mixed with sodium chloride and mechanically activated in a ball mill. The activated mixture is treated with water at about 90 °C while stirring. This dissolves the lithium. The lithium-rich slurry is filtered and purified. The extracted lithium is finally processed into lithium hydroxide. Since no strong acids are used and energy consumption is lower, this process is also considered more environmentally friendly.

Direct acid digestion and other promising processes

Several renowned research institutes are working on the direct use of α-spodumene without the energy-intensive detour via calcination.

Direct acid digestion of α-spodumene, in which it is mixed directly with concentrated sulphuric acid at 200 to 250 °C, is considered a potentially more efficient process. This produces soluble lithium sulphate. However, acid consumption is very high, which entails safety risks. In addition, the sulphate-containing wastewater must be cleaned at great expense. Compared to calcination, however, the process saves 30 to 50 percent energy. The more compact process would be particularly advantageous for the decentralised utilisation of spodumene in small plants. This process has not yet been used commercially.

A process developed by Penn State University has been patented. It uses a combination of microwave roasting with the addition of sodium hydroxide, which converts α-spodumene into a soluble phase. It is then leached with water. The technology is being further developed in collaboration with Hertz Energy and is expected to enter the pilot phase soon. Energy consumption and thus CO₂ emissions are significantly lower than with calcination-based processes. Another advantage would be the less complex plant with fewer process units.

Conclusion and outlook: It can also be more environmentally friendly

The extraction of lithium hydroxide from spodumene concentrate by calcination and acid digestion is a common practice. However, the high-temperature calcination process for phase conversion from α- to β-spodumene is very energy-intensive and associated with high greenhouse gas emissions. Using concentrated sulphuric acid also pollutes the environment and requires considerable investment in equipment. For new plants to be accepted, especially in Europe, it is essential that they operate more sustainably. Modern processes either aim to reduce acid use (e.g. Metso and Tesla) or eliminate the need for calcination (Hertz Energy).

Extracting lithium from brine has several advantages over the calcination method. Direct lithium extraction from lithium-containing groundwater, ideally powered by renewable energy, is considered to be the way forward. This method has a significantly lower environmental impact than conventional lithium extraction in evaporation ponds because the brine is returned to the aquifer once the lithium has been extracted.

You can find out more about this in part 2 of the article series 'How does lithium extraction actually work?', which will be published in June 2025.

Author

Dr. Ulla Reutner

Chemist and freelance specialised journalist