Custom electrodialysis setup. Credit: Jorge Vidal/Rice University
A new membrane marks an important step toward more efficient extraction of lithium which is needed for reusable batteries. The design can also be used to extract other essential elements like cobalt and nickel.
“Our goal was to develop a material that can extract lithium with minimum environmental impact,” says Qilin Li, co-director of Rice University’s Nanotechnology Enabled Water Treatment (NEWT) Centre, USA.
“The smart design principles we used to develop the membrane architecture have ensured it can be adapted to help recover many other valuable resources from various waste streams.”
Currently, it is estimated that 87% of the lithium extracted is used to create batteries like those used in electric vehicles, laptops and smartphones. This lithium is commonly extracted from saltwater lakes or brines through an inefficient process that involves evaporation and chemical treatments.
“The most widely used large-scale lithium extraction method today requires massive evaporation ponds and chemical precipitation,” says Li.
“The process can take over a year to reach the target concentration and has fairly low lithium recovery rates. It also uses a lot of water, often in places that already experience water scarcity, and produces considerable amounts of chemical waste.”
The membrane developed by the team extracts lithium using considerably less energy, while maintaining higher selectivity.
The membrane collects lithium through a process called electrodialysis. An electrical current is applied to the brine which pushes lithium ions to pass through the membrane, whilst other elements like sodium, calcium and magnesium get left behind.
“Typically, when you apply an electrical field, all the positively charged ions will transport across the cation exchange membrane,” says Li.
“Lithium is actually a minor component in brine, but our membrane allows primarily lithium to transport across. Other ions stay behind.”
The team were able to create such an effective membrane by inserting nanoparticles of lithium titanium oxide (LTO) into it. The crystal structure of LTO is the perfect size for lithium ions to move across without allowing for other elements to pass through.
The researchers embedded nanoparticles of lithium titanium oxide (LTO) into the membrane. Credit: Jorge Vidal/Rice University
The study, published in Nature Communications, shows the membrane is less energy-intensive than the typical electrodialysis process used in industry. It also maintained its performance after 2 weeks of use and degradation.
The membrane contains 3 layers which the team can individually optimise to also extract other valuable minerals like cobalt and nickel.
“One of the important features of our membranes is their potential to be produced at scale, which could pave the way for their use in industrial settings,” says Jun Lou, a professor of material science and nanoengineering.