Sustainable Lithium from Domestic Sources

Lithium is a key raw material for the energy transition and is primarily used in lithium-ion batteries for electric vehicles, electronic devices, and energy storage systems. Global demand for lithium is expected to increase sixfold by 2030, which increases the strategic importance of domestic resources in Germany and Europe. In the ThermIon project, Fraunhofer ISE is working with partners from science and industry to develop a new process for the selective extraction of lithium from geothermal sources.

Initial Situation

Geothermal brines are typically used for energy purposes. This ranges from simple applications in thermal baths and heating networks to the generation of electricity from high-enthalpy geothermal sources. Geothermal brines contain a variety of dissolved metal ionsminerals and gases, which pose a very complex challenge for utilization from a geochemical perspective. The brines must not be cooled too much and must remain under pressure to prevent outgassing and precipitation and ensure that all minerals metal ions remain in solution. In order to extract lithium, processes must therefore be developed that extract only lithium in a highly selective manner and leave all other conditions of the brines unaffected. Such processes are referred to as direct lithium extraction (DLE) processes. Electrochemical extraction processes, such as the lithium-ion pump, are considered an extremely promising approach, but still need to be transferred from the laboratory to industrial scale.

Objective

Although various process approaches for extracting lithium from thermal water are already under development, no market-ready technology is available as yet. "ThermIon" aims to develop and demonstrate an environmentally friendly, economically attractive, and innovative extraction technology suitable for lithium. The entire process chain will be taken into account, from the pretreatment of the brine, through lithium extraction and lithium carbonate or lithium hydroxide crystallization, to the controlled recirculation of the brine. To this end, the research team will first evaluate the lithium resources in the geothermal aquifers of the Upper Rhine Graben in terms of sustainability and economic viability using geohydrological investigations and simulations.

Approach

The challenge lies in selectively extracting lithium from these geothermal waters without disrupting the complex geochemical balance, for example through changes in pressure or pH and without risking the precipitation of other substances such as silicates and calcite. The latters would also involve considerable technical risks for the operation of the geothermal plant, as their precipitation would lead to deposits and thus to an impairment of the hydraulic and thermal operating parameters.

"ThermIon" is therefore further developing direct lithium extraction (DLE) technology, as this extracts only the lithium from the brine in a highly selective manner, leaving the other elements untouched. The particular challenge for DLE technologies is to operate them over long periods of time even at high temperatures and very high pressures of up to 30 bar. The research team is focusing on the “lithium ion pump” process, for which the team has conducted initial preliminary tests in the laboratory. Driven by an electric field, this “pump” stores lithium ions in a special lithium manganese oxide electrode and releases them back into a recovery solution when the polarity is reversed. This allows a concentrated lithium chloride solution with a high degree of purity to be obtained.

Interim Results

In a first step, we transferred the “lithium-ion pump” process from the beaker experiment to an automated cycle test bench with multiple channels. Continuous operation enables the collection of extensive datasets under standardized conditions and allows conclusions to be drawn about the long-term stability of the materials used. In an initial long-term test, 900 extraction cycles have already been demonstrated, with further potential for optimization, for example through lower charging rates or gentler voltage ranges.

Further progress has also been made at the reactor level. While fixed-bed reactors or reactors with flow-through of the active material (“packed-bed” or “flow-through”) enable increased lithium uptake through improved mass transport, they are associated with high pressure losses, uneven overflow profiles, and increased flushing costs. By adapting the electrodes to the “flow-by” design known from membrane technology, in which the fluid flows along and not through, low packing densities and low hydraulic pressure losses can be achieved, which reduces the pumping energy requirement and at the same time enables effective flushing procedures with comparable lithium uptake. In addition, applying the electrode paste using a screen-printing process results in a more homogeneous surface and improved flow in the reactor.

• BWG Geochemische Beratung GmbH
• Deutsche ErdWärme GmbH
• DVGW-Forschungsstelle am EBI des KIT
• Hydroisotop GmbH
• Karlsruher Institut für Technologie (KIT) – Department of Geothermal Research
• K-UTEC AG Salt Technologies
• Universität Bremen – Chair of Energy Storage and Energy 
• Conversion Systems
• VKTA – Strahlenschutz, Analytik & Entsorgung Rossendorf e.V.

The “ReNew” project is funded by the Federal Ministry of Economic Affairs and Energy (BMWE).