**6. Conclusions**

In this study, a new waterjet-based recycling process for traction battery cells is presented. This direct recycling process detaches the cathode material of a battery cell from the carrier foil with the aid of a water jet. An advantage of this procedure over indirect approaches is that the recovered recyclate can be mixed with new cathode material directly, and therefore energy-intensive manufacturing steps for the admixed fraction can be saved. In addition, the cells or modules are not shredded or melted down, as in conventional recycling processes, but are dismantled to the cellular level, and therefore the pure battery components can be separated by type.

Furthermore, the waterjet-based recycling approach was ecologically evaluated with the help of a life cycle assessment (LCA). The aim is to evaluate its potential ecological performance as compared with indirect recycling approaches and virgin cathode material with the focus on global warming potential (GWP). The results from this study provide an initial assessment of the ecological performance of this recycling approach. A comparison with indirect recycling processes shows that the GWP associated with indirect recycling of traction batteries (TBs) can be reduced by a factor up to 26 through substitution with this direct recycling approach. Compared to cathode coating from production with primary raw materials, the recyclate obtained through the waterjet-based recycling process shows 100 times less GWP. Consequently, the GWP of new battery cells can be significantly reduced through admixture of recyclate obtained through the waterjet-based recycling process. The data basis of the water-based recycling process for the LCA is consistent, as the data are provided first-hand from the recycling company. However, a critical review of the life cycle analysis in this study shows that with the focus on recycling the cathode material, the further battery components are not included. They should be added to the assessment scope in upcoming LCAs to gain a holistic picture of the ecological performance of this process.

From an ecological point of view, the waterjet-based recycling approach can be classified as more environmentally friendly than conventional hydro- or pyrometallurgical recycling processes. Due to the effective ecological performance of this recycling approach, the technical limits should be explored and tested. It also needs to be clarified whether the process can be used for future cell chemistry to fully exploit the given potential of this recycling approach in the long term.

**Author Contributions:** Conceptualization, F.R. and R.W.; methodology, F.R., I.K.; software, L.K.; validation, A.S., F.R.; formal analysis, I.K. and F.R.; investigation, M.S., M.F. and F.R.; resources, M.S. and R.W.; data curation, M.S. and L.K.; writing—original draft preparation, L.K. and M.F.; writing—review and editing, F.R. and I.K; visualization, F.R. and L.K.; supervision, R.W., F.R. and A.S.; project administration, R.W. and I.K.; funding acquisition, R.W. and L.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors wish to thank the Ministry of the Environment, Climate Protection and the Energy Sector Baden-Wuerttemberg for funding this work under the funding code L7520105 as part of the joint project "DeMoBat". The article processing charge was funded by the Baden Wuerttemberg Ministry of Science, Research and the Arts and the Hochschule Esslingen—University of Applied Sciences in the funding program Open Access Publishing.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on reasonable request from the corresponding author.

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

#### **References**

