Lithium-ion batteries have been extensively used in various applications owing to their advantages and high-performance. Typically, they are made up of organic electrolytes, plastics, metals, among other materials. Owing to current stringent measures on sustainability and environmental protection, recycling of valuable metals has attracted significant research attention. Apart from being toxic and a great contributor to the rapid surge in the solid-waste related problems, these metals are valuable and naturally scarce, hence the need to recycle and reuse them. For instance, the cathode materials of ternary batteries contain non-ferrous materials such as nickel, cobalt, and manganese that can be recycled and reused in developing new batteries.
Among the techniques developed to recover valuable metals from lithium-ion batteries, solvent extraction has been identified as a promising technique for separating a mixture of cobalt, nickel, and manganese from LiNixCoyMnzO2 cathode materials. It makes use of the difference in the chemical properties of the metals. This method can also be used to obtain high-quality products through multistage separation. Unfortunately, most of the available extractants are not effective and do not improve the shortcomings of the process. To address the above challenges, Dr. Tianchi Liu, Professor Ji Chen, Hailian Li, and Kai Li from the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences developed a novel integrated process for the separation and recovery of valuable metals from spent LiNi0.5Co0.2Mn0.3O2 cathode materials. Mainly, the separation process involved a combination of leaching, cascade extraction, and precipitation methods. Their research work is currently published in the journal, Separation and Purification Technology.
In their approach, a mixture of 2 mol/L sulfuric acid and 3 vol% hydrogen peroxide reagents were used as leaching agents for the leaching of different metals. Then, the cascade extraction was explicitly used to separate lithium, nickel, cobalt, and manganese using di-(2-ethylhexyl) phosphinic acid (P227) and di-(2-ethylhexyl) phosphoric acid (P204) extractants. Meanwhile, their high purity solid products such as MnO2, Li2CO3, NiO and Co3O4 were also obtained depending on the precipitation procedure. Finally, the overall recovery process of LiNi0.5Co0.2Mn0.3O2 was evaluated to establish the feasibility of the proposed approach.
The authors achieved a leaching rate above 99% for all the metals, which enabled them to obtain high-quality nickel, lithium, manganese and cobalt products. Consequently, they noted that the separation of different metals required different and specific optimal conditions. For instance, one-step extraction was used to separate lithium-nickel and cobalt-manganese by P227, four-stage extraction was used to separate cobalt-manganese by P204, while five-stage extraction was used to separate lithium-nickel by P227. Moreover, high purity solid products were obtained and the final yield for lithium, nickel, cobalt, and manganese was found to be 96.15/100%, 91.54/98%, 91.15/93% and 91.56/100%, respectively.
In summary, the authors reported the design of an integrated process to recover Li, Ni, Mn, and Co metals from LiNi0.5Co0.2Mn0.3O2 cathode materials using P227 and P204 extractants for the first time. Results showed a high recovery yield above 90% for all the solid products. In a statement to Advances in Engineering, Professor Ji Chen said their study provided important theoretical guidance for the development of more effective methods for the separation and recovery of valuable metals from waste lithium-ion batteries.
Liu, T., Chen, J., Li, H., & Li, K. (2020). An integrated process for the separation and recovery of valuable metals from the spent LiNi0.5Co0.2Mn0.3O2 cathode materials. Separation and Purification Technology, 245, 116869.