Although the magnets for electric motors are manufactured under expensive and environmentally unfriendly conditions, scrap magnets have so far hardly been recycled and reused. Scientists have now developed a new recycling method that produces new ones from old magnets without any major loss of performance. The process, which can be implemented on a large scale and can be varied depending on requirements, could promote the use of such recycling magnets in e-mobility.
The expansion of electromobility is an important step in the energy transition and should help to reduce CO2 emissions in the long term. According to the federal government’s plans, seven to ten million electric vehicles are to be registered by 2030. However, this also means that more and more electric motors and the high-performance permanent magnets that are essential for their function are required. They make up about half of the engine costs and contain rare earth metals such as neodymium or dysprosium, among other things. The mining of these rare earths takes place mainly in China and releases toxic by-products, among other things, which contaminate the groundwater and thus harm people and nature.
Is it a magnet or can it go away?
But although the magnets are produced under such expensive and environmentally harmful conditions, no sustainable recycling processes exist to date. Instead, the used magnets usually end up in the scrap yard and are melted down there with other residual metal. Materials scientist Konrad Opelt and his team from the Fraunhofer Institute for Material Cycles and Resource Strategies in Hanau want to change that. In order to prove that electric motors with recycled old magnets can achieve the same performance as with new magnets, the scientists first created an e-bike, an e-scooter and a hoverboard.
“For all new vehicles, we first characterized the engine in detail in order to obtain relevant parameters with which we can later compare the performance of the engines with the recycled magnets,” reports Opelt. They received the old magnets for their recycling process from various industrial partners, which means that they differ significantly in terms of performance, shape and quality – Opelt and his team want to stay as close to reality as possible and show that the recycling process can also work with very different starting materials.
From old to new
When recycling old magnets, their material is crushed and exposed to a hydrogen atmosphere. The penetrating hydrogen causes the material to break down into granules, which are further comminuted with a jet mill. This powder can then be put into a mold and “baked” into the new magnet. The decisive advantage: While the starting material has to be melted down when new magnets are manufactured, which consumes a great deal of energy, this is no longer necessary with old magnets. Mere chopping is enough. “We can easily skip the environmentally harmful mining of the raw materials and the energy-intensive melting,” explains Opelt.
Theoretically, thousands of magnets can be processed simultaneously in this recycling process. However, it can hardly be prevented that the magnets come into contact with some oxygen, which slightly reduces the performance. “However, we can counteract this in a targeted manner, for example by adding ten to twenty percent new material or further processing the microstructure of the magnets,” says Opelt. The performance of the magnets can then be determined on the finished end product or even at the powder stage. The researchers are currently still in the process of further optimizing the treatment process during the recycling process. However, Konrad Opelt is confident that they will soon be able to install the recycled magnets in electric motors.
Recycling becomes individual
In the future, the researchers also want to enable application-specific recycling variants by deriving a property portfolio from their analyzes of the recycled magnets. This should help future users to be able to adapt the recycling processes to their needs in such a way that specific magnetic properties can be achieved depending on the material composition. If scrap metal recycling actually finds widespread application, it would be a crucial step in building a value chain that is not only sustainable, but also makes e-mobility less dependent on resources. Opelt hopes that in the future, manufacturers will make sure that the magnets can be easily removed and reinstalled during the production of electric motors – and thus make recycling possible.
Source: Fraunhofer Institute for Material Cycles and Resource Strategies IWKS