Battery recycling: Used tyres for lithium-ion batteries

14. Nov 2022 | Industry + More

However you look at it: Despite investments in alternatives such as e-fuels, the battery electric vehicle is currently the mobility of the future. Despite some contradictions. After all, electric vehicles are not (yet?) completely environmentally friendly or even sustainable. The Fraunhofer Institute is now working on optimising lithium-ion batteries to make electric cars of the future more climate-friendly. The keyword here is recycling.

To put it positively: There is still room for improvement in terms of the energy balance for the production of electric car batteries and electric motors. Raw materials are shipped all over the world and further processing and production is anything but climate-neutral: Around 80 percent of the globally mined lithium comes from Chile, Australia and Argentina, for example. It is often processed in China.

Cobalt, which largely comes from the Democratic Republic of the Congo and is required for the positive pole of most electric cars, is seen as particularly problematic. After all, there are frequent reports of child labour in the mines in the Congo.

All raw materials also cause high water consumption and severe water contamination. Another problem: The high-tech materials in the lithium-ion batteries installed in the cars can currently only be partially recycled and with considerable effort.

Optimising the lithium-ion battery to make it more environmentally friendly

This is precisely what a consortium consisting of experts from the Fraunhofer Institute and industrial companies are working on: Together, the partners aim to optimise the lithium-ion battery from an environmental perspective to make future electric cars more climate-friendly. "The goals are far-reaching: Batteries should not only be produced using more sustainable processes, but must also be more resistant to thermal decomposition and thus safer," explains the Fraunhofer Institute. "And making batteries completely recyclable is a further focus of the development work. However, the new battery should also deliver on performance and, by adapting the electrolytes, be able to offer high power even at low temperatures."

While the industrial partners of the consortium are focussing on the electrolytes, the research facilities are optimising the electrodes. "For example, the anode consists of a highly porous carbon aerogel (…) to be made from sustainable bio-resources," explain Christian Kaiser and Dr. Sebastian Dittrich, heads of the working group "Preparation and recycling" at the Fraunhofer Institute for Building Physics. To improve conductivity, this aerogel is combined with a carbon black prepared by the Fraunhofer IBP. The special feature: The researchers don't use a newly produced carbon black in this process, but recycle it from used tyres.

Carbon black from used tyres

The problem with recycled carbon black: It is contaminated and cannot be used without treatment. For this reason, the researchers have developed a special cleaning procedure that makes the carbon black suitable for use in tyre production. As part of the project, the cleaning procedure is now to be further optimised and the purity achieved increased to an extent that the recovered carbon black can also be used in the lithium-ion batteries. In addition to recovering the carbon black from used tyres, the researchers also want to design electrodes and electrolytes in such a way that they can be recycled at the end of the battery life.

Comprehensive and practical evaluation of the potential

Particular attention needs to be paid to comprehensive, practical consideration and evaluation of potential: The life cycle assessment is therefore just as important as the envisaged production on an industrial scale. The team of experts keeps a constant eye on the cost-effectiveness of the process. A pilot plant at the Fraunhofer IBP is also already in planning. The aim is to use the developed technology in the form of a battery as an application example in a laptop or an electric car. All components will then be completely recycled. The project is due to run until 2025.