Eutectic freeze crystallization for NiSO4 recovery in the recycling of Li-ion batteries

A M.Sc. Thesis Project in Chemical Engineering at the Division of Resource Recovery

Background:

With the ever-growing need for lithium-ion batteries (LiBs), particularly from the electric mobility industry, a large amount of LiBs is bound to retire soon, thereby leading to serious disposal problems and detrimental impacts on the environment and energy conservation [1]. For the recycling of LiBs, the foils of Cu and Al and the anode material are easily physically separated. The composition of the cathode material is complex and rich in valuable metals, and thus a key to viable recycling is to “close the loop” of the cathode material. The recovery of cathode material using a hydrometallurgical process has been widely studied. It includes leaching (e.g. acid leaching, bioleaching, etc.), separation and purification (e.g. solvent extraction, chemical precipitation, electrochemical deposition, etc.), and production of metal salts (e.g. crystallization, precipitation, etc.) [2].

Nickel sulfate is critically important in certain electric vehicle battery cathodes, particularly for battery technologies using nickel-cobalt-manganese (NMC) and nickel-cobalt-aluminium (NCA) cathodes [3]. In the recycling of NMC and NCA LiBs, evaporative crystallization (EC) is usually employed to produce NiSO₄·6H₂O after solvent extraction, but it is not energy-efficient. Eutectic freeze crystallization (EFC), a low-temperature technique, has been recently investigated for the recovery of NiSO₄, and it shows uses much less energy and has the ability to recover pure water and treat corrosive streams [4]. This technique is based on cooling a concentrated aqueous salt stream down to the eutectic point of the respective salt–water system, where salt crystals and ice crystals are formed simultaneously. If EFC is used to produce battery-grade NiSO₄ in the recycling of LiBs, further investigation is needed to control the impurity level in the NiSO₄product.

The project

In the PERLI (Processes for Efficient Recycling of Lithium Ion Batteries) project funded by the Swedish Energy Agency, we are currently developing an efficient process to recover valuable metals from spent LiBs [5]. The recovery of Co, Ni and Mn sulfate salts of high purity using EFC is a part of the process. Preliminary experiments have demonstrated promising results. This degree project will investigate the EFC of NiSO₄ from a solution stream with impurity and find the conditions to reduce the impurity content in the resulting salt. The project contributes to an energy-saving crystallization technique for NiSO₄ recovery and improves product purity in the recycling of LiBs. It is supervised by Drs. Yiqian Ma, Michael Svärd and Kerstin Forsberg, and carried out in collaboration with both industrial and academic partners.

The work will include: 

1. Literature studies on EFC.
2. Determination of relevant solubility or phase diagrams.
3. Performance of batch crystallization experiments for NiSO₄ recovery.
4. Investigation of the behavior of impurity and characterization of products.
5. Report writing.

For questions or to express your interest, please contact:

Yiqian Ma (yiqianm@kth.se) or Kerstin Forsberg (kerstino@kth.se)

Reference:

[1] Huang, B., Pan, Z., Su, X., & An, L. (2018). Recycling of lithium-ion batteries: Recent advances and perspectives. Journal of Power Sources, 399, 274-286.

[2] Ma, Y., Svärd, M., Xiao, X., Gardner, J. M., Olsson, R. T., & Forsberg, K. (2020). Precipitation and Crystallization Used in the Production of Metal Salts for Li-Ion Battery Materials: A Review. Metals, 10(12), 1609.

[3] Lewrén, A. (2019). Life cycle assessment of nickel-rich lithium-ion battery for electric vehicles A comparatative LCA between the cathode chemistries NMC 333 and NMC 622.

[4] Ma, Y., Svärd, M., Gardner, J., Olsson, R. T., & Forsberg, K. (2021). Application of Eutectic Freeze Crystallization in the Recycling of Li-Ion Batteries. In Rare Metal Technology 2021 (pp. 3-10). Springer International Publishing.

[5] https://www.kth.se/sv/ket/resource-recovery/recycling-of-batteries-1.938983