Recycling of Li-Ion batteries — The effects of mechanical activation on valuable metals leachability from the black mass of NMC 111

In the coming years, the electric-vehicle (EV) market is expected to grow considerably, leading to increased battery waste. For that reason, this work presents a suitable process for battery recycling, focused on extracting valuable metals from nickel-manganese-cobalt (NMC) spent batteries. To achieve the metal extraction, the proposed methodology involves mechanical activation as a pretreatment stage, followed by acid leaching. In this study, parameters such as milling time, leaching agent concentration, and temperature were analyzed. The optimal experimental conditions were 1,000 rpm and 60 min of milling time, 2 M sulfuric acid (H2SO4), 60 °C and 120 min of leaching time. These conditions ensured 98 percent lithium and 80 percent or greater cobalt, manganese and nickel dissolution. It is important to highlight that copper and aluminum impurities were also extracted; however, these metallic traces did not affect the leachability of valuable metals. Background It has been demonstrated that hydrometallurgical techniques, coupled with physical treatments, ensure the dissolution of valuable metals from spent batteries [1]. However, there are aspects that need to be addressed; for example, in NMC battery treatment, basically, when acidic solutions are used, extracting manganese, cobalt and nickel is more challenging than extracting lithium. Lv et al. [2], determined that lithium can be first released from the crystal structure and interacts with hydronium ions (H+). Then, cobalt, manganese and nickel react, progressively destroying the crystal structure. Another relevant aspect is the possibility of impurity dissolution, such as copper and aluminum, which influence the leaching selectivity. Therefore, in this study, mechanical activation and acid leaching are analyzed. Mechanical activation is a proficient technique that allows breaking the atomic bonds in the crystal lattice of the solid, promoting high leaching efficiencies in acidic solutions. Moreover, the study of impurity dissolution and its impact on the extraction of valuable metals is also presented. Finally, this work suggests an alternative solution for developing more efficient recycling techniques. Methods Mechanical activation: milling. The physical treatment was performed using the Vibratory Disc Mill RS 200 by Retsch. The equipment functioned using horizontal vibrations generated by a 1.5-kW three-phase motor. The tests were carried out using 50 g of black mass sample (per batch), at two speeds (700 and 1,000 rpm) and with three different times (2, 8 and 60 min). Fig. 1 Leaching efficiency of cobalt, manganese, nickel, lithium, copper and aluminum in the 2 M H2SO4 system at 60 °C:(a) untreated sample, (b) mechanically treated sample(1,000 rpm, 60 min). Acid leaching. Sulfuric acid solutions (H2SO4, 97 percent) were prepared to process the black mass sample (solid-to-liquid ratio of 50 g/L). Three double-walled, 100-mL MEAB PVDF reactors were used. All the experiments were performed in triplicate, and the parameters studied were H2SO4 concentration (1 and 2 M) and temperature (25 and 60 °C). The samples were analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES, Thermo Fisher Scientific, Model iCAP 6000 Series). Results and discussion Table 1 shows the chemical composition of the NMC black mass sample, untreated and mechanically treated. The data for the treated sample correspond to high-speed milling at 1,000 rpm for 60 min, as these conditions promoted efficient leaching yield. The primary metals in the samples were cobalt (Co), nickel (Ni), manganese (Mn) and lithium (Li), though traces of copper (Cu), aluminum (Al) and iron (Fe) were also detected. Leaching experiments were conducted at different temperatures and leaching agent concentrations. Nevertheless, this report focuses on results under optimal conditions, where valuable metals were efficiently extracted. Thus, Fig. 1 shows the leaching yields of Co, Mn, Ni, Li, Cu and Al as a function of time at 2 M H2SO4 and 60 °C. When the tests were carried out using untreated samples, the leaching efficiencies were 91 percent Li, 58 percent Co, and 61 percent Ni and Mn, respectively (Fig. 1a). On the other hand, when the sample was activated mechanically, the leaching yields for all metals improved. In this case, the leaching efficiencies were 98 percent Li, 81 percent Co, 84 percent Ni and 80 percent Mn (Fig. 1b). Specifically, the lithium extraction rate was faster and reached equilibrium after 30 min, whereas the dissolution of Mn, Co and Ni was slower. The incomplete dissolution of cobalt, manganese and nickel is due to these metals reacting partially with the sulfate ion (SO42−) compared to lithium [3]. However, mechanical activation significantly enhanced metal liberation, yielding 80 percent or greater leaching for Co, Ni and Mn, whereas Li was almost completely leached. Finally, Cu and Al were extracted in high percentages in both systems (Fig. 1), but they did not affect the extraction of valuable metals. Understanding the behavior of undesirable metal ions in pregnant leach solutions is essential, as it helps determine the refinement stages and the number of purification phases required for a global recycling process. Conclusion This work demonstrated that physical treatments, especially mechanical activation, improved the extraction of valuable metals from NMC spent batteries using sulfuric acid solutions. High speeds and milling time, as well as acid media, allowed 98 percent Li and 80 percent or greater of Co, Ni and Mn extraction. The proposed methodology provides a basis for understanding the dissolution of valuable metals and impurities, emphasizing that the use of coupled techniques is required to improve recycling processes. Funding This research was supported by the ÅForsk (Grant: 22-182) and BASE (Batteries Sweden) by the VINNOVA via 2024-03853. Selected references Guan J, Xiao H, Lou X, Guo Y, Luo X, Li Y, Yan C, Yan X, Gao G, Yuan H, Dai J, Su R, Gu W, Guo Z (2018). Enhanced hydrometallurgical recovery of valuable metals from spent lithium-ion batteries by mechanical ESEE 80–88 Lv W, Wang Z, Cao H, Zheng X, Jin W, Zhang Y, Sun Z (2018). A sustainable process for metal recycling from spent lithium-ion batteries using ammonium chloride. Waste Manag 79:545–553 Lin J, Fan E, Liu C, Zhang X, Cao H, Sun Z, Chen R (2020). Conversion mechanisms of selective extraction of lithium from spent Lithium-ion batteries by sulfation roasting. ACS Appl Mater Interfaces 12:18482–18489

Recycling of Li-Ion batteries — The effects of mechanical activation on valuable metals leachability from the black mass of NMC 111

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