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Localisation of lithium deposits using multi-parameter approaches

Lithium (Li) has been classified by the European Union as a strategically critical raw material since 2023 under the Critical Raw Materials Act, which means that by 2030 at least 10% of these raw materials should be mined in the EU and no more than 65% should be dependent on a third country.

This poses a challenge, as the demand for storage solutions with a higher energy density is continuously increasing due to the energy transition and steadily increasing technologisation and, on the other hand, 33% of the total production of lithium is controlled by Chinese investors. The demand for lithium, one of the raw materials used in rechargeable batteries, is expected to triple by 2035. According to a 2018 study by the Federal Agency for Nature Conservation, 40,000 tonnes of this raw material alone will be needed to achieve the German government’s target of six million electric vehicles by 2030. This is supported by the EU Battery Regulation, which came into force on 18 February 2024 and sets requirements for the sustainable extraction of lithium and the recycling of used batteries, among other things. Nevertheless, the majority of lithium demand must still be covered by primary raw materials. In addition to mining in Australia, extraction from salt lake brines is highest in South American countries. Lithium extraction from salt lakes is often criticised, as social conflicts and environmental damage arise primarily due to the high water requirements.

Calibration of the ion chromatography columns. A clear separation of the interfering element sodium can be recognised.

With regard to the Critical Raw Materials Act, the EU Battery Regulation and the Supply Chain Act, which describes the corporate responsibility for compliance with human rights within the supply chain, it would be a great advantage to recognise from which type of deposit (secondary deposits such as salt lake brines from lithium chloride or primary deposits from lithium pegmatites) the lithium was extracted or even if the deposit region could be narrowed down. Lithium is the lightest element that is in a solid state at room temperature. It has two isotopes (6Li (7.4 %) and 7Li (92.6 %)) with a mass difference of over 10 %. This ensures a very large so-called isotopic fractionation of δ7Li of up to 60 ‰ in natural samples, which is controlled by natural processes such as dissolution and precipitation reactions. Paired with possibly characteristic trace element patterns, Li isotope analysis is the most promising approach to characterise different deposits and thus possibly to be able to make a statement at least about the type of deposit.

Li isotope analysis of reference materials with different lithium isotope ratios.

Thanks to our intensive research at CEZA, we have extensive experience in the development and application of such multi-parameter approaches. We have been able to establish and verify a lithium isotope analysis method using ion chromatography that is capable of separating lithium from all interfering accompanying elements, mainly sodium, from spodumene samples in less than three hours. This makes it the fastest separation method for lithium to date (Fig. 1). Using our HR-MC-ICP-MS (High Resolution Multi Collector – Inductively Coupled Plasma Mass Spectrometer), we were able to carry out initial measurements of both standards (Fig. 2) and spodumene samples (Fig. 3) with a high degree of reproducibility. We were able to show that spodumene samples can sometimes have the same δ7Li value, but also significant differences of at least 8 ‰. This shows that Li isotope analysis has the potential to be used for deposit characterisation.

Isotope analyses of three mineral separates containing the lithium mineral spodumene.