**5. Conclusions**

This paper described the first step of an approach, designated as functional recycling, to recover NMC material from the cathodes of end-of-life Li-ion batteries or scrap from the production of cathodes, while preserving its chemical, physical, and morphological properties. The separation of the cathode coating from the Al substrate foil can be performed in a neutral or alkaline medium, with minimal mechanical treatment. However, several chemical side reactions and side effects, such as the release of Li, the formation of a passivation layer, or the disintegration of the secondary NMC particles, were identified to have a crucial effect on the quality of the recovered NMC material. Furthermore, this paper demonstrated the emerging challenges to the analytical methods and tools to detect the smallest changes in the material, to develop the most efficient and environmentally friendly route to recover NMC for re-use in Li-ion batteries.

**Author Contributions:** Conceptualization, J.D. and J.A.; methodology, J.D., A.R., T.S., and J.A.; leaching experiments, J.D., A.R., and T.S.; Raman and SEM-EDX investigation, T.S. and T.L.; formal analysis, T.S. and T.L.; supervision, J.A.; all authors contributed to the production of the manuscript.

**Funding:** This research was funded by Bundesministerium für Bildung und Forschung (BMBF) under gran<sup>t</sup> number 16SBS007.

**Conflicts of Interest:** The authors declare no conflict of interest.
