## 4 Conclusions  
The analysis of the presented research results allowed for the following conclusions to be drawn:  
1. The leaching efficiency of cobalt and other valuable components from the battery masses increases with increasing concentrations of sulfuric acid in the range from 15% to 20%, with the addition of 1 dm\({}^{3}\) or 2 dm\({}^{3}\) of hydrogen peroxide;
2. The leaching of a 1 kg portion of the battery mass (regardless of the material composition) in the 15% or 20% sulfuric acid solution with the addition of 1 dm\({}^{3}\) or 2 dm\({}^{3}\) of H\({}_{2}\)O\({}_{2}\), for 2 h, with a solid-to-liquid-phase ratio of 1:5 (or even 1:4) at 60 \({}^{\circ}\)C ensures a leaching efficiency of cobalt, nickel, copper and lithium above 95%;
3. The use of the two-stage counter-current leaching of the battery mass in the selected conditions ensures the leaching efficiency of cobalt, nickel, copper and lithium at a level significantly above 95%, while obtaining the concentration of cobalt in the  
Figure 4: XRD analyses of the masses after leaching—Material I and Material III.  
after-leading solution at a level of nearly 50 g/dm\({}^{3}\), reducing the duration of leaching in a single stage up to 1 h and, most importantly, reducing the amount of waste solutions and the consumption of H\({}_{2}\)O\({}_{2}\) and sulfuric acid.  
The above-mentioned data made it possible to formulate a patent application for the method of conducting the two-stage leaching process of the battery masses and to consider implementing the process of acid leaching of the battery masses in industrial conditions by Elemental Strategic Metals Ltd. (Grodzisk Mazowiecki, Poland) [59].  
Conceptualization, K.L-S., M.Z., M.O., A.C., D.K., G.B., P.L., A.S.-T. and A.F.; methodology, M.Z., K.L.-S., M.O., D.K., P.L. and A.S.-T.; software, K.L.-S. and K.G.; validation, K.L.-S., A.C., P.L., A.S.-T. and D.K.; formal analysis, P.L., A.S.-T., K.L.-S., D.K., M.O. and A.P.; investigation, D.K., M.O., A.P. and A.S.-T.; resources, P.L. and A.S.-T.; data curation, D.K., M.O. and A.P.; writing--original draft preparation, K.L.-S., K.G., P.L. and A.S.-T.; writing--review and editing, K.L.-S., D.K., P.L., A.S.-T. and A.F.; visualization, M.O., A.P. and K.G.; supervision, K.L.-S., A.C. and P.L.; funding acquisition, K.L.-S. and M.Z. All authors have read and agreed to the published version of the manuscript.  
This research has been co-financed by the European Union according to the EC decision C (2019) 8823 of 9 December 2019, within call no. 8/1.1.1/2020--Fast track--IPCEI organized by the Polish National Centre for Research and Development.  
Not applicable.  
Data Availability Statement: Data is contained within the article.  
Acknowledgments: Elemental Strategic Metals Sp. z o.o. implements the project: \"Research, development and first industrial deployment of innovative technologies of Li-Ion batteries and spent autocatalysts recycling with recovery of strategic metals\", comprising the development of technologies for the safe, environmentally friendly and cost-effective transport, storage and recycling of Li-ion batteries and other waste with strategic metal contents. ESM's project has been co-financed by the European Union according to the EC decision C (2019) 8823 of 9 December 2019, within call No. 8/1.1.1/2020--Fast track--IPCEI organized by the Polish National Centre for Research and Development.  
Authors [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] were employed by the company Lukasiewicz Research Network--Institute of Non-Ferrous Metals. Author [PERSON] and [PERSON] were employed by the company Elemental Strategic Metals Sp. z o.o. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.  
References