In Saudi Arabia, researchers have developed a cell and membrane that extract lithium ions from seawater. The collected material is said to be clean enough to be used by the battery industry.
The supply of lithium is limited and the high price of the raw material is a factor behind the search for a cheaper battery chemistry. The forecast is also that the land-based reserve is expected to be depleted by 2080.
The amount of lithium in the sea is at best 0.2 parts per million (ppm), but a number of research projects have worked on methods to extract the element from the water – including in Japan. Now King Abdullah University of Science and Technology (Kaust) developed a technology that is said to make extraction at a low cost.
It is an electrochemical cell with a ceramic membrane consisting of lithium-lanthanum-titanium oxide (LLTO). Seawater is taken into the cell’s main chamber and lithium ions pass through the membrane to collect in a side space. The openings in the membrane structure are so small that larger metal ions are kept out. In the side compartment there is a buffer solution that maintains a stable pH value, as well as a copper cathode coated with platinum and ruthenium.
With anion exchange and membrane filtration, the negative ions are passed to a third chamber containing a sodium chloride solution and a platinum-ruthenium anode. At a voltage of 3.25 volts, the cell generates hydrogen at the cathode and chlorine gas at the anode – this in turn drives the transport of lithium through the LLTO membrane.
The researchers started from the water in the Red Sea. After five enrichment cycles, the water in the cell reached a lithium amount of 9,000 ppm. Thanks to the adjustment of the pH value of the solution, the lithium is clean enough to be used in battery production.
According to the researchers, this is the first time that a so-called LLTO membrane has been used to collect and concentrate lithium. Their work is published in Energy & Environmental Science. Now they will continue to work with the optimization of the membrane and the design of the cell.