A team of Rice University researchers led by Lisa Biswal and Haotian Wang has developed an innovative electrochemical reactor to extract lithium from natural brine solutions, offering a promising approach to address the growing demand for lithium used in rechargeable batteries. This breakthrough, published in the Proceedings of the National Academy of Sciences , holds significant potential for renewable energy storage and electric vehicles.
Lithium is a critical component in batteries for renewable energy storage and electric vehicles, but traditional lithium extraction methods have faced numerous challenges, including high energy requirements and difficulty separating lithium from other elements. Natural brines - salty water found in geothermal environments - have become an attractive lithium source, because traditional ore sources are increasingly difficult and expensive to mine. However, these brines also contain other ions like sodium, potassium, magnesium and calcium, which have very similar chemical properties to lithium, making efficient separation extremely challenging. The similarity in ionic size and charge between lithium and these other ions means that traditional separation techniques often struggle to achieve high selectivity, leading to additional energy consumption and chemical waste. Moreover, brines contain high concentrations of chloride ions that can lead to the production of hazardous chlorine gas in traditional electrochemical processes, adding further complexity and safety concerns to the extraction process.
The Rice engineering team has tackled these challenges with a novel three-chamber electrochemical reactor that improves the selectivity and efficiency of lithium extraction from brines. Unlike traditional methods, this new reactor introduces a middle chamber containing a porous solid electrolyte - think of interconnected highways - that prevents these unwanted reactions by controlling ion flow as the brine passes through. The cation exchange membrane acts as a barrier to chloride ions, preventing them from reaching the electrode area where they could combine to produce chlorine gas and thereby minimizing hazardous by-products. The key component that enables highly selective lithium extraction lies in the specialized lithium-ion conductive glass ceramic (LICGC) membrane on the other side of the electrolyzer, which selectively allows lithium to pass through while blocking other ions. The LICGC membrane's high ionic conductivity and selectivity are crucial for maintaining efficiency as it significantly reduces the interference from the other ions present in natural brines such as potassium, magnesium and calcium. Although LICGC membranes are typically used in solid-state lithium-ion batteries, this application for selective extraction of lithium represents a novel and efficient use of the material's high ionic conductivity and selectivity.
"Our approach not only achieves high lithium purity but also mitigates the environmental risks associated with traditional extraction methods," said first author Yuge Feng, a graduate student in the Biswal lab . "The reactor we created is designed to minimize by-product formation and improve lithium selectivity."
The reactor achieved impressive results, including a lithium purity rate of 97.5%. This means the setup could effectively separate lithium from other ions in the brine, which is critical for producing high-quality lithium hydroxide, an important material for battery manufacturing. In addition, the new reactor design significantly reduced the production of chlorine gas, making the process safer and more environmentally friendly. The researchers said it has the potential to be a game changer for lithium extraction from challenging sources like geothermal brines.
"This reactor could represent a major step forward in making lithium extraction both more efficient and less harmful to the environment," said Biswal, the William M. McCardell Professor in Chemical Engineering and co-corresponding author with Wang.
Another key finding related to challenges with the reactor's stability over time. The team observed that sodium ions, unlike potassium, magnesium or calcium, tended to build up on the LICGC membrane surface, which hindered lithium transport and increased energy consumption. While this buildup could affect the efficiency of lithium extraction, the researchers identified strategies to mitigate this issue, such as lowering the current levels, and suggested that future research explore surface coatings or current pulsing to further optimize the reactor.
By offering a cleaner, more efficient and potentially faster method for extracting lithium from geothermal brines, this research marks an important step toward ensuring a steady supply of lithium for renewable energy technologies.
"Our field has long struggled with the inefficiencies and environmental impacts of lithium extraction," said Wang, associate professor of chemical and biomolecular engineering. "This reactor is a testament to the power of combining fundamental science with engineering ingenuity to solve real-world problems."
Graduate students contributing to this study from Rice's Department of Chemical and Biomolecular Engineering include Feng, Yoon Park, Chang Qiu, Feng-Yang Chen, Peng Zhu and Quan Nguyen. Postdoctoral fellows from the same department are Shaoyun Hao, Zhiwei Fang, Xiao Zhang and Shoukun Zhang. Tanguy Terlier serves as the director of surface and interface characterization at the SIMS Laboratory within Rice's Shared Equipment Authority.
The research was supported by Rice University and the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE) under Award DE-EE0010881. The content in this press release is solely the responsibility of the authors and does not necessarily represent the official views of the supporting entities.
