Breakthrough sun-powered tech pulls lithium from seawater, redefining energy

Researchers have developed a sustainable method to efficiently extract lithium from seawater, addressing the growing demand for renewable energy.

The Solar Transpiration-Powered Lithium Extraction and Storage (STLES) device harnesses sunlight to extract and store lithium from brine.

The method uses iron phosphate electrodes, which have the ability to selectively capture lithium ions from salt water. Once absorbed, the electrodes release the lithium into fresh water, making the extraction process both efficient and environmentally friendly.

According to researchers from Nanjing University and the University of California, Berkeley, the approach offers a cleaner alternative to traditional lithium mining, which often involves harmful chemical processes and significant land disruption.

The work is similar to research done by a University of Chicago team using iron phosphate particles to efficiently extract lithium from seawater, groundwater, and flowback water.

Cleaner lithium technology

Vigorous research into more effective lithium sourcing has been spurred by the importance of lithium batteries to the infrastructure supporting renewable energy sources.

Lithium extraction from seawater has long been attractive, but it faces challenges due to the low concentration of lithium and the presence of other minerals like magnesium and calcium. Seawater contains 230 billion tonnes of lithium, but separating it has been costly—over 10 times more expensive than other methods.

“The sustainability of lithium-based energy storage or conversion systems, e.g., lithium-ion batteries, can be enhanced by establishing methods of efficient lithium extraction from harsh brines,” said the team, in the study abstract.

A recent method for lithium extraction , inspired by battery technology, uses iron phosphate electrodes to selectively capture lithium from salt water and release it into fresh water. Silver oxidation and reduction at counter electrodes maintain charge balance, keeping other cations on the salt side.

Another approach draws inspiration from plants, employing a solar transpirational evaporator to extract, store, and release lithium using sunlight. These innovations offer promising techniques for efficient and sustainable lithium recovery, addressing the growing demand for lithium in renewable energy storage systems.

Membrane-free recovery

In the new study, researchers developed a membrane-free electrochemical cell that separates lithium ions between two compartments: one filled with brine and the other with fresh water.

These compartments are isolated from each other but remain connected through silver/silver-halide redox electrodes, enabling the efficient cycling of lithium ions.

Iron-phosphate electrodes capture and release the lithium , making the system effective and easy to operate without the need for a membrane to keep the liquids apart.

Long-term tests have shown the device’s stability, compatibility, and scalability. Operating passively without extra energy input, the system is both cost-effective and eco-friendly. It can also integrate with existing evaporation ponds, reducing installation costs and enabling the treatment of hypersaline brines with high osmotic pressure.

The new design also works with harsh brines, even those with high magnesium levels and very low lithium concentrations, and can still produce over 99.95 percent pure lithium carbonate suitable for batteries.

Researchers claim that it saves up to 21.5 percent in energy by efficiently using the osmotic energy from the brines. In a pilot test, a larger cell with an electrode area of 33.75 square meters was used to extract lithium from Dead Sea brine, achieving a recovery rate of 84 percent.

While these technologies show potential at laboratory and pilot scales, their economic viability and environmental impact in commercial applications need further assessment.

According to the team, a key challenge is to optimize extraction efficiency while minimizing water use and land disruption, as the materials involved can be expensive and may require more affordable alternatives.

The details of the team’s research were published in the journal Science .