Recovery of Mn and Co from industrially processed Lithium-Ion Batteries using Solvent Extraction and investigation of the saponification process for Cyanex 272

Licentiatavhandling, 2025

The electrification of the transport sector is one of the main efforts undertaken by nowadays society to minimize the emission of greenhouse gases. The number of electric vehicles on the road is increasing, and with them the quantity of lithium-ion batteries (LIBs) introduced on the market. As the lifetime of LIBs ranges between 10-15 years, a significant quantity of end-of-life batteries are expected to be available soon. The hazardousness of such a waste, together with the significant content of valuable metals and the necessity of preserving the primary sources of critical metals (e.g., Li, Co, Mn, Ni etc.) have been the main driver for the development of recycling strategies for LIBs. Among the alternatives proposed, hydrometallurgy has the potential to ensure high recovery efficiency and high purity products which can be reused for LIBs production. Within this recycling approach, solvent extraction has shown to have the potential to efficiently recover of Mn, Co and Ni. Within this thesis, the recovery of these transition metals from end-of-life LIBs by solvent extraction is further investigated.
The first work focuses on the recovery of Mn as high purity (99.6 ± 0.1%) MnSO4·H2O from purified NMC111 lithium-ion batteries leachate using solvent extraction and evaporative crystallization. 98% of Mn was recovered using 35% v/v D2EHPA in Isopar L in three counter-current stages at pH = 2.9 ± 0.1 and θ = 1. As Co, Ni and Li were partially co-extracted, two scrubbing stages with a solution of Mn 4 g/L (70 mM) at θ = 1 were necessary to purify the extract. A product containing 8.8 g/L of Mn with a relative purity of 99.5 ± 0.1% was obtained after two stripping stages using 0.5 M H2SO4 and at θ = 1. From such product MnSO4·H2O was crystallized using evaporative crystallization. The distribution of impurities such as Ca, Zn, Mg, Na, Si and Al in the solvent extraction circuit was also studied.
The second work investigates the extraction of Co. As pH control during counter-current extraction confirmed to be a challenging operation, saponified Cyanex 272 was in this case used. However, a lack of clarity regarding the selection of saponification conditions and a lack of information regarding the accuracy of the McCabe-Thiele method when a saponified solvent is used was found in the literature. Therefore, beside focusing on achieving an efficient Co recovery, the selection of suitable saponification conditions ([NaOH], T) are discussed, together with the use of saponified solvents in multi-stage extraction. Efficient (99.8%) Co recovery from an NMC9.5.5 purified leachate could be achieved in two counter-current stages using 45% Saponified 0.3 M Cyanex 272 in Isopar L.