While lithium extraction technologies generally focus on ways to get the essential metal out of the ground, there's another source to mine: existing batteries that no longer work. A new technique could now make that process economically viable.
When it comes to energy storage in rechargeable batteries, it's hard to beat lithium. As the lightest metal on the period table, it has an impressive energy density. It also sheds electrons more easily than any other metal, meaning it has the highest electrochemical potential. Additionally, it excels at storing and releasing energy repeatedly. Yet, while lithium is abundant on our planet, mining clean sources of it can be difficult, costly, and environmentally damaging.
So, to find other sources of the material, scientists have been turning to lithium-ion batteries that have reached the end of their lifespan, yet still have perfectly usable amounts of the metal inside. Last year, for example, we heard about a method of using microwaves to free up the lithium inside spent batteries. Still, even though spent batteries are in abundant supply, separating out the lithium from the other materials they contain can also be an expensive proposition.
Enter the new technique from scientists at the University of Illinois Urbana-Champaign. There, a team led by chemical and biomolecular engineering professor Xiao Su, has been spending time disassembling batteries and then submerging them in an organic solvent. This leads to a brine that contains lithium as well as other metals present in the batteries.
To harvest the lithium, the team developed a special electrode created from a copolymer consisting of molecules that attach to lithium and those that respond to an electrical current. When placed inside the brine and electrified, it sucked only lithium from the solution like a sponge, leaving other metals behind.
Not only was the method effective at separating out and recovering lithium, but the electrode was able to maintain its conductivity for over 500 cycles. What's more, the researchers say the method is much more affordable than other battery-based lithium-harvesting techniques, costing about US$12.70 per kilogram of lithium recovered.
That's in comparison to acid leaching, which runs about $81-462 per kilogram and produces chemical waste, and high-heat smelting, which costs $36-126 per kilogram and is more inefficient at separating out lithium from other elements. Based on these findings, the team says its method could be the first commercially viable way to recapture lithium from dead batteries.
Indeed, according to Daily Metal Prices, lithium costs $13.17 per kilo on the open market as of the time of writing. So this method actually comes out cheaper than just buying the stuff.
The researchers indicate that their work was designed as a proof-of-concept study and believe more efforts should now be put into scaling and refining their discovery.
"These results help highlight the broad applicability of electrochemical separations for metal recycling, not only in water, but also from organic solvents that are commonly used to leach waste batteries," concludes Su. "We envision this work helping establish a more circular, sustainable supply chain for lithium, enhancing supply security and potentially reducing the environmental impacts associated with other forms of lithium extraction, such as mining."
The study has been published in the journal ACS Energy Letters.
