Substitution: The search for new resources

Rare, expensive, harmful to the environment – a number of research projects aim to use more sustainable alternatives instead of critical raw materials. But simply replacing A with B is not always the best solution.

By Eva Augsten

In 2020, new registrations for electric cars skyrocketed. In Germany alone, the government wanted to put 15 million e-cars on the roads by 2030, each of which will require around 5 kg of pure lithium for its battery. Electric vehicles were also booming in other countries. “There will not be enough lithium available to achieve these targets,” warned Handelsblatt at the time, based on data from the Federal Institute for Geosciences and Natural Resources. The market supported this fear. The price of a ton of the lithium ore spodumene shot up from less than USD 1,000 in 2021 to over USD 6,000 at the end of 2022. The silvery-white metal, which hardly anyone except ceramic manufacturers had been interested in, quickly became a symbol of critical raw materials in the eyes of the public.

For some, the lithium shortage was proof that electromobility cannot work – for others, it was a reason to look for alternatives. A widely promoted option was sodium, a component of table salt, and similarly easy to extract from the sea or mines. In 2023, the Fraunhofer Research Institution for Battery Cell Production FFB drew up a detailed inventory of all aspects of the sodium-ion battery. Its structure is similar to that of lithium-ion batteries, so the facilities in the research factory could also be used to develop and scale up production processes for sodium-ion batteries. Although its energy density would never come close to the established lithium competition due to the material, the sodium-ion battery promised advantages not only in terms of sustainability and fire safety, but above all in terms of price. In China in particular, manufacturers secured patents and announced gigafactories for sodium batteries. The target markets were any applications where minimal costs were more important than low weight: stationary storage units, e-scooters and inexpensive small cars. The sodium battery, Fraunhofer FBB concluded from its data, was “here to stay”.

But things turned out differently. Investors were quickly found who wanted to supply the coveted lithium and earn big money with it. Australia in particular increased its production rapidly. On the consumer side, however, growth was slower than expected and speculators soon disappeared from the market. The peak at the end of 2022 was followed by a sudden drop in lithium prices. The price advantage of the sodium-ion battery dissolved like salt in the sea.

And when it comes to safety and sustainability, researchers are also finding it difficult to speak of an advantage of sodium ion batteries. This is because lithium-ion batteries have also been making rapid progress. Lithium iron phosphate (LFP) is increasingly replacing the previously dominant combination of lithium nickel manganese cobalt oxide (NMC) as a cathode material and ensures greater fire safety. “The ecologically really problematic raw materials nickel and in some cases even cobalt can still be found in the sodium ion battery, although not necessarily – but not in the LFP battery,” says Florian Degen, Division Director, Strategy and Corporate Development at Fraunhofer FFB.

Coltan, manganese and cobalt are mined in the Mudere mine in the Democratic Republic of the Congo. Experts consider occupational health and safety in such mines to be problematic.

| Erberto Zani / stock.adobe.com

“Cobalt is a particular problem in small-scale mining in the Congo for health and safety reasons. There is physically enough lithium on earth; environmental and social criteria must play an important role in the development of the respective deposits,” adds Matthias Buchert, Head of the Resources & Transport Division at the Öko-Institut. In addition to lithium, as the name suggests, the lithium iron phosphate battery essentially contains the abundantly available iron and phosphate – previously known primarily as a fertilizer: almost 50 million tons are spread on fields worldwide every year.

In terms of safety and energy density, solid-state batteries based on lithium could bring even further improvements. It is clear to most experts that lithium will remain the dominant material for electricity storage in mobility for the foreseeable future.

Matthias Buchert, Head of the Resources & Transport Division at the Öko-Institut

| Öko-Institut

There are other reasons not to become too fixated on avoiding a single raw material. After all, if you turn one adjusting screw, other parameters change automatically, explains Buchert. One example of this is electric motors. The magnets in electric synchronous motors – whether in cars or in servos in industry – contain a high proportion of rare earths by mass. This is mainly neodymium, but also dysprosium and terbium, which ensure temperature stability, among other things. Switching to asynchronous motors would immediately eliminate the need for these materials, but it would come at a price. “Compared to asynchronous motors, permanently excited synchronous motors tend to be more efficient, more compact and easier to control,” says Buchert. In generators for wind energy, there is even a trend away from robust asynchronous generators towards synchronous generators. They enable material-saving designs without gears and the targeted provision of reactive power. At the same time, however, manufacturers are working on reducing the amount of critical materials in generators and motors. “In recent years, the use of the so-called heavy rare earths dysprosium and terbium, which were particularly critical, has been reduced,” says Buchert.

Another example is PEM electrolyzers. They are often used to generate hydrogen from wind and solar power due to their flexibility and are dependent on iridium as a catalyst material. The material is more or less a by-product of platinum mining, with mining companies extracting less than ten tons a year from the earth. The metal specialist Hereaus hopes that catalysts based on ruthenium could reduce the need for iridium by up to 85 percent. However, the production of ruthenium is only three to four times higher than that of iridium. So we're still a long way from an optimal solution here too. “When it comes to reducing critical raw materials, there is usually no black and white, but a long road to ever lighter gray,” summarizes Buchert.