Electric cars (and just about anything else that runs on lithium batteries) aren’t all that “green” because producing the mineral comes at a huge cost to the planet. Now Stanford scientists say they’ve discovered a way to extract lithium from brine solutions that’s more efficient, half the cost and greener than current methods.
This is good news because with electric vehicles and renewable energy storage systems, societies will need much more lithium. It is estimated that the automotive industry alone will need 20 times more. Conventional extraction requires a lot of energy, land and water (about 500,000 liters per tonne of lithium).
The vast majority of lithium used in batteries currently comes from hard rock mining in places like the Salar de Atacama in Chile. Extraction time is about 18 months: First, mineral-rich brine must be extracted and pumped into evaporation ponds of up to 26 square kilometers each. Solar radiation evaporates this brine, which is pumped from pond to pond as its chemical concentration increases. It is then collected and sent to be refined and the lithium recovered. Traditional processes achieve a lithium recovery rate of 40%.
Researchers at Stanford’s School of Engineering, led by Professor Yi Cui, have developed a method called redox couple electrodialysis (RCE). It works by using electricity to transport lithium from water with a low concentration of the metal to a higher concentration solution, passing it through a solid-state electrolytic membrane. This is done through a series of cells. In each of these cells, the lithium concentration increases to a point where it is easy to isolate it.
This method has numerous advantages:
- Use only one tenth of the electricity.
- Recovering almost 100% of lithiumis extremely efficient.
- It typically costs around €10,000 to extract a tonne of lithium from brine. RCE can do this for around €4-5,000, half the cost.
- Eliminates the need for large ponds evaporation, which would reduce the environmental impact of extraction
- Related to this is expanding the number of viable lithium brine sources around the world. The brine found in North America or Europe is harder to work with because of the toxic materials it contains (it needs higher boiling points). CER could make more extraction sites viable and profitable.
The Stanford team’s RCE follows in the footsteps of another green method called DLE, which relies on adsorbents. In it, lithium salts from a mineral-rich brine bind to the surface of a resin and can be washed off the resin with water. They say it’s more than 90% efficient and doesn’t require an expensive acid to bind the lithium to an inert material. But this new RCE method is even more effective.
As always when we talk about innovation, we now have to see if the RCE process can be applied on a large scale to meet demand, how it can be optimized for fast and safe extraction, and whether it can be applied to seawater containing lithium salts. It does have the potential to satisfy our enormous appetite for lithium.
