A team of Rice University researchers led by Sibani 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.”