Solid state electrolyte for greener lithium production
Researchers in the US have found that the electrolyte used in solid state batteries can also be used to filter lithium ions as part of the production process.
The team at Rice University found that the solid state electrolyte, which allows lithium ions to move in the battery, also acts as a suitable membrane material for aqueous lithium extraction, separating out the ions and water.
To make lithium extraction more environmentally sustainable, researchers have been exploring direct extraction technologies that recover the material from unconventional sources such as oil- and gas-produced water, industrial wastewater and geothermal brines. These methods, however, have struggled with ion selectivity, particularly when trying to separate lithium from other ions of similar size or charge like magnesium and sodium.
The discovery presents a potential breakthrough in sustainable resource recovery, reducing reliance on traditional mining and extraction techniques that are both time-consuming and environmentally damaging and boosting other sources such as brine and recycling schemes.
“The challenge is not just about increasing lithium production but about doing so in a way that is both sustainable and economically viable,” said Prof Menachem Elimelech at Rice University.
The novel approach developed by Elimelech and his team hinges on a fundamental difference between SSEs and conventional nanoporous membranes. Whereas traditional membranes rely on hydrated nanoscale pores to transport ions, SSEs shuttle lithium ions through an anhydrous hopping mechanism within a highly ordered crystalline lattice.
“This means that lithium ions can migrate through the membrane while other competing ions, and even water, are effectively blocked,” said researcher Sohum Patel, who is now a postdoctoral researcher at the Massachusetts Institute of Technology. “The extreme selectivity offered by our SSE-based approach makes it a highly efficient method for lithium harvesting as energy is only expended towards moving the desired lithium ions across the membrane.”
In tests with high concentrations of competing ions, the solid state electrolyte consistently demonstrated near-perfect lithium selectivity with no detectable competing ions in the product stream. This is something conventional membrane technologies have been unable to achieve.
Using a combination of computational and experimental techniques, the team investigated why the SSEs showed high selectivity. The rigid and tightly packed crystalline lattice of the SSE prevented water molecules and larger ions like sodium from passing through the membrane structure. Magnesium ions, which have a different charge than lithium ions, were also found to be incompatible with the crystal structure and were rejected.
“The lattice acts as a molecular sieve, allowing only lithium ions to pass through,” said Elimelech. “This combination of highly precise size and charge exclusion is what makes the SSE membrane so unique.”
The researchers noted that while competing ions did not penetrate the SSE, their presence in the feed solution reduced lithium flux by blocking available surface sites for ion exchange, a challenge they believe can be addressed through further material engineering.
“By integrating SSEs into electrodialysis systems, we could enable direct lithium extraction from a range of aqueous sources, reducing the need for large evaporation ponds and chemical-intensive purification steps,” said Patel. “This could significantly lower the environmental footprint of lithium production while making the process more efficient.”
The findings also suggest broader applications for the electrolyte in ion-selective separations. “The mechanisms of ion selectivity in SSEs could inspire the development of similar membranes for extracting other critical elements from water sources,” said Elimelech. “This could open the door to a new class of membrane materials for resource recovery.”
If you enjoyed this article, you will like the following ones: don't miss them by subscribing to :
