The demand for lithium on Earth is so great that it could soon become a global problem. Its resources on the planet are extremely limited, while the demand for this basic raw material for battery production is constantly growing. One solution to the problem of lithium deficiency may be its extraction from used batteries. However, this is still an extremely costly, dirty and very lengthy process. But it can be accelerated, scientists say.
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Researchers at Rice University have been working to create a green technology for extracting lithium from used batteries. They started by borrowing a solvent recipe from the field of green chemistry. Chemists, like all other environmentally concerned scientists, were looking for something safer for the environment for reactions with solvents. Such a discovery was the discovery of deep eutectic solvents (DES or DES, in English) in the early 2000s. These are environmentally friendly liquids that have proven capable of precipitating lithium and other metals from solution.
«The rate of [traditional] reduction is very slow because lithium is usually the last metal to precipitate after all the other metals, so our goal was to figure out how we could target lithium specifically,” explained Salma Alhashim, who is one of the lead authors. research. “Here we used DES, which is a mixture of choline chloride and ethylene glycol, knowing from our previous work that during leaching in this DES, lithium becomes surrounded by chloride ions from the choline chloride and leaches into solution.”
But this was only a partial solution to the problem of accelerated recovery of lithium from solution. In general, the property of choline chloride was known to be enhanced absorption of microwave radiation by this compound. And this became a great catalyst for the process! The researchers were able to isolate lithium almost 100 times faster than in a traditional oil bath. In fact, it only took them 15 minutes to recover 87% of the lithium, a process that would have taken 12 hours using an oil bath.
«This allowed us to selectively leach lithium over other metals,” said Sohini Bhattacharyya, another lead author of the work. “Using microwaves for this process is similar to how a kitchen microwave quickly heats up food. The energy is transferred directly to the molecules, causing the reaction to occur much faster than with conventional heating methods.”
Because the chemistry of DES solvents is flexible enough, they can be configured to extract other elements from solutions, such as cobalt or nickel. The process turns out to be so clean and fast that it could make a big difference in future lithium battery supply and recycling chains.