The MERCATOR project investigated the feasibility of using graphite recovered from end‑of‑life lithium‑ion batteries as a secondary resource for several industrial applications. The study focused on three main use cases: anode material for new lithium‑ion cells, carbon source (aufkohlungsmittel) in steel production, and filler in polymer composites. The research combined experimental testing of the recycled material with process optimisation and techno‑economic assessment.

In the battery‑anode tests, recycled graphite was fabricated into electrode slurries and assembled into coin‑cell prototypes. Capacity measurements showed that the recycled material delivered a specific capacity that was lower than that of reference graphite electrodes, indicating some degradation during the recycling process. However, cycling tests up to 200 charge‑discharge cycles revealed a relatively stable capacity retention, suggesting that the material could still be viable for secondary battery applications after further optimisation. Discharge‑current measurements indicated that the internal resistance of the recycled‑graphite electrodes was slightly higher than that of the reference electrodes, but within acceptable limits for many commercial cell designs. Density and electrical‑resistance tests confirmed that the recycled graphite possessed a bulk density comparable to commercial graphite, while the resistivity remained below the threshold required for high‑power applications.

For the steel‑making application, the recycled graphite was introduced as a carbon additive in a laboratory‑scale melting experiment. The fine‑powdered nature of the material led to prolonged melt times and incomplete dissolution, preventing the target carbon content from being achieved. These results highlighted the need for improved handling and pre‑treatment of the recycled graphite to enhance its solubility in molten steel. The study also identified that alternative melting conditions, such as higher temperatures or longer soak times, could potentially improve the incorporation of the carbon.

In polymer composites, recycled graphite was blended with a thermoplastic matrix to evaluate its reinforcing effect. Mechanical testing of the resulting composites showed a modest increase in tensile strength and modulus compared with unfilled polymer, while maintaining good processability. The filler also contributed to a slight reduction in electrical resistivity, indicating potential for conductive composite applications.

The project’s collaboration network comprised a mix of industry and academia. Accurec GmbH, a mid‑size recycling company, provided the recycled graphite feedstock and operated the pilot‑scale recycling line. The Institute for Metallurgical Process Technology and Metal Recycling (IME) at the University of Aachen supplied expertise in pyro‑ and hydrometallurgical recycling concepts and conducted the battery‑anode experiments. UVR‑FIA GmbH from Freiberg contributed to the polymer composite development and mechanical testing. The consortium worked under the auspices of the German Federal Ministry of Education and Research (BMBF) and received additional support from the European Commission’s Horizon programme. The project ran over a multi‑year period, with the initial pilot plant established in 2015 and the final report compiled in 2020.

Overall, the MERCATOR study demonstrated that recycled graphite can serve as a promising secondary resource, but its performance depends strongly on the specific application and the quality of the feedstock. The findings provide a solid foundation for scaling up the recycling process, refining the material properties, and integrating recycled graphite into commercial production chains, thereby advancing the circular economy for battery materials.