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Press Release of November 5, 2021

When batteries become foam

HZDR PhD student with concept for improved battery recycling at Falling Walls competition

Foto: Anna Vanderbruggen im Labor ©Copyright: HZDR/HIF

HIF PhD student Anna Vanderbruggen is highly motivated to convince the jury at the future competition Falling Walls in Berlin with her innovative concept for recycling lithium-ion batteries.

Source: HZDR/HIF


Efficiently recycling batteries and reintegrating the recovered materials into production is still an apparently unsolvable problem for industry. That's why researchers around the world are looking for new approaches. One of them is Anna Vanderbruggen. The PhD student at the Helmholtz Institute for Resource Technology Freiberg (HIF) - an institution of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) - developed a concept to recycle graphite from used lithium-ion batteries. On November 7th, she will present her approach in the final of the future competition Falling Walls in Berlin.

Electro mobility increases the demand for lithium-ion batteries - and leads to an enormous global demand for critical materials such as nickel, cobalt, lithium and natural graphite, which, on the other hand, are not infinitely available on our planet, and, on the other hand, are often mined under poor conditions. Therefore, the development of efficient recycling technologies and the integration of the recovered materials into battery cell production is absolutely essential. The goal is to close material cycles with efficient approaches.

A very relevant but also very critical material for lithium-ion batteries is graphite. Due to the energy transition in the mobility sector, graphite will remain one of the determining materials in battery production in the coming decades. However, natural deposits of graphite that can be mined economically are rare. Furthermore, recycling companies are currently unable to recover graphite. Therefore, it ends up as waste or is used as a reductant agent during the recycling process. Anna Vanderbruggen has taken up this challenge and developed a concept for "recovering graphite from spent lithium ion batteries", which is also the subject of her PhD thesis.

“My approach uses the method of froth flotation, which is proven in the raw materials industry, to recycle graphite. Froth flotation is an established and efficient process for separating valuable minerals from waste rock for particle sizes of about 10 to 200 micrometer. The process is based on the selective hydrophobisation, i.e. water-repellent property, of minerals and the adhesion of these particles to gas bubbles, which are subsequently discharged via a foam. Therefore, surface properties, but also other particle properties such as size and morphology, are the key separation characteristics for froth flotation. Adding a froth flotation stage allows the metals and graphite to be recovered together,” Anna Vanderbruggen explains her concept.

It is precisely such forward-looking ideas that are sought in the annual Falling Walls competition. The competition, which is aimed at young inventors, researchers, start-up entrepreneurs and students, is affiliated with the Falling Walls Conference in Berlin. This took place for the first time in 2009 on the anniversary of the fall of the Berlin Wall and has the motto “Tearing down walls and overcoming borders: In Minds, in Thoughts and in Action”. Anna Vanderbruggen first prevailed in the national competition of the Falling Walls Lab and thus secured her participation in the International final in Berlin on November 7th. Then the Frenchwoman has to convince the jury with her 3-minute short presentation of her future idea of battery recycling to become “Breakthrough Winner of the Year in the Emerging Talents category of Falling Walls”. The winner will receive a cash prize and will have the opportunity to give their presentation again in front of a large audience at the Falling Walls Conference on November 9th.

The Falling Walls Conference is funded by the Federal Ministry of Education and Research (BMBF), the Helmholtz Association and the Robert Bosch Foundation. In addition, a large number of scientific institutions and foundations are participating, including acatech – German Academy of Science and Engineering, the Leibniz Association, the Fraunhofer Society, the Max Planck Society, the Donors' Association for the Promotion of Sciences and Humanities in Germany, the German Academic Exchange Service (DAAD), the Körber Foundation, the Leopoldina – National Academy of Sciences and Humanities, the Berlin Senate Department for Education, Science and Research as well as the European Research Council.

Livestream of the Falling Walls Final with Anna Vanderbruggen:

Sunday, November 7, 2021, 9 - 11 a.m.

Further Information:

Dr. Martin Rudolph | Department Head Processing
Helmholtz Institute Freiberg for Resource Technology at HZDR
Phone: +49 351 260 4410 | Email:

Anna Vanderbruggen | PhD student at Department Processing
Helmholtz Institute Freiberg for Resource Technology at HZDR
Phone: +49 351 260 4416 | Email:

Press Contact:

Anne-Kristin Jentzsch | Press Officer
Helmholtz Institute Freiberg for Resource Technology at HZDR
Phone: +49 351 260 4429 | Email: