The new technology is estimated to be able to extract lithium from saltwater at less than 40% of the cost of current mainstream extraction methods and just a quarter of lithium's current market price. According to a study published today in Matter by Stanford University researchers, the new technique is far more reliable and sustainable than current techniques in terms of water, chemical and land use.
Global demand for lithium has soared in recent years due to the popularity of electric vehicles and renewable energy. Currently, the primary method of lithium extraction involves pouring saltwater into giant ponds and leaving it in the sun for over a year to evaporate, leaving behind a lithium-rich solution, then using large amounts of toxic chemicals to complete the process. Highly salty water containing lithium occurs naturally in some lakes, hot springs and aquifers, and also as a by-product of oil and natural gas extraction and desalinization.
“The inherent efficiency and cost advantages of our approach make it a viable alternative to current extraction techniques and have the potential to revolutionize the lithium supply chain.”
Senior author Yi Cui, professor of materials science and engineering
Many scientists are exploring cheaper, more efficient, reliable and environmentally friendly methods of lithium extraction. These are typically direct lithium extraction, which bypasses large evaporation ponds. A new study reports results and cost estimates for a new method using an approach called “redox coupled electrodialysis,” or RCE.
“The inherent efficiency and cost advantages of our approach make it a promising alternative to current extraction techniques and have the potential to revolutionize the lithium supply chain,” said Yi Cui, lead author of the study and professor of materials science and engineering in the College of Engineering.
The team estimates that their method would cost $3,500 to $4,400 per tonne of high-purity lithium hydroxide, which can then be cheaply converted into battery-grade lithium carbonate. By comparison, mainstream technologies to extract lithium from brine cost about $9,100 per tonne. The current market price for battery-grade lithium carbonate is about $15,000 per tonne, but supply shortages in late 2022 have pushed volatile lithium market prices up to $80,000.
Meeting growing demand
Lithium has played a key role in the global transition to sustainable energy so far: Demand for lithium is expected to grow from around 500,000 tonnes in 2021 to 3-4 million tonnes by 2030, according to a report by McKinsey & Company. This sharp increase is mainly driven by the rapid adoption of electric vehicles and renewable energy storage systems, which rely heavily on batteries.
Traditionally, lithium has been extracted from mined rocks, but this method is even more expensive than brine extraction, is energy intensive, and uses toxic chemicals. As a result, the current predominant method of lithium extraction has switched to evaporating the brine from salt lakes, which still incurs high economic and environmental costs. This method is also highly dependent on specific climatic conditions, and there are only a limited number of commercially viable salt lakes, raising doubts about whether the lithium industry can keep up with the growing demand.
The new method developed by Choi and his team uses electricity to move lithium from water with low lithium concentrations through a solid electrolyte membrane into a more concentrated, pure solution. Each cell in the series increases the lithium concentration, making the final solution relatively easy to chemically separate. The method uses less than 10% of the electricity required for current brine extraction techniques and is highly efficient, with lithium selectivity approaching 100%.
“The advantages of our approach over conventional lithium extraction techniques increase the feasibility of environmentally friendly and cost-effective lithium production,” said Rong Xu, co-first author of the study, a former postdoctoral researcher in the Cui lab and now a professor at Xi'an Jiaotong University in China. “Ultimately, we hope that our method will significantly advance electrified transportation and renewable energy storage capabilities.”
Cost and Environmental Benefits
The study includes a simple techno-economic analysis comparing the costs of current lithium extraction with those of the RCE approach. The new method is expected to be relatively inexpensive, mainly due to lower capital costs. It eliminates the need for large solar evaporation ponds, which are expensive to build and maintain. In addition to sustainability benefits, the new method uses significantly less electricity, water and chemicals, further reducing costs.
The RCE approach also reduces the environmental footprint of lithium production by avoiding the extensive land use and water consumption of conventional methods.
The RCE method can be used with a variety of brines with different concentrations of lithium, sodium and potassium. Laboratory experiments have shown that the new technology can extract lithium from wastewater from oil production, for example. The technique could also be used to extract lithium from seawater, which has a lower lithium concentration than brine. Extracting lithium from seawater by conventional methods is not currently commercially viable.
“Direct lithium extraction technologies like ours have been in development for some time. To date, the main competing technologies have significant drawbacks, including inability to operate continuously, high energy costs, and relatively low efficiency,” said Ge Zhang, a postdoctoral researcher at Stanford University and co-author of the study. “Our method does not appear to suffer from any of these drawbacks. Continuous operation could contribute to more reliable lithium supplies, helping to calm volatile lithium markets.”
Looking to the future
The scalability of the RCE method is also promising: in experiments where the device was scaled up by a factor of four, the RCE method continued to perform well, with both the energy efficiency and lithium selectivity remaining very high.
“This suggests that the method could be applied on an industrial scale and could be a viable alternative to current extraction techniques,” Choi said.
Still, the study highlights an area where further research and development is needed. The researchers tried two versions of their method: one that extracted lithium faster and used more power; another that was slower and used less power. Compared to the faster extraction, the slower extraction resulted in lower costs and a more stable membrane for continuous, long-term extraction of lithium. Under high current densities and faster water flow, the membrane degraded and became less efficient over time. This was not evident in the slower extraction experiments, but the researchers hope to optimize the device design to enable faster extraction. They are already testing other promising materials for the membrane.
The researchers also did not demonstrate extraction of lithium from seawater in this study.
“In principle, our method could be applied to seawater, but there may be problems with membrane stability in seawater,” Zhang said.
Nevertheless, the team remains very optimistic.
“As research progresses, we believe our method can quickly be transferred from the lab to large-scale industrial applications,” Xu said.
More Information
The study's other co-first author, Xin Xiao, was a postdoctoral researcher at Stanford University at the time the research was conducted and is now a faculty member at Zhejiang University. The other co-authors are Yusheng Ye, Pu Zhang, Yufei Yang and Sanzeeda Baig Shuchi, all at Stanford. Yi Cui is the Fortinet Founders Professor of Engineering, Dean of the Sustainability Accelerator at Stanford's Doerr School of Sustainability, a professor of Energy Science and Engineering and Photon Science, a senior fellow and former director of the Precourt Institute for Energy, and a senior fellow at the Woods Institute for the Environment. This research was funded by the StorageX Initiative, an industry-related program within Stanford's Precourt Institute for Energy.
