An investigation into the synergistic enhancement of MIBK for lithium extraction utilizing the TBP–FeCl3 system from spent LiFePO4 powder

In the field of lithium-ion battery (LIB) recycling, solvent extraction has emerged as a research hotspot due to its numerous advantages such as room-temperature operation, environmental protection and low energy consumption; however, the relatively low single extraction efficiency remains a considerable challenge for its large-scale application. In this study, we employ an optimized extraction system utilizing methyl isobutyl ketone (MIBK) as a synergist with tributyl phosphate (TBP)–FeCl₃ to simultaneously extract lithium and iron from the leaching solution of spent LiFePO₄ powder. This method achieves a secondary extraction rate of lithium as high as 97.6%. Additionally, FTIR spectroscopy analysis reveals notable changes in the chemical bonds PO, CO, and P–O–C, as well as shifts in the characteristic peak of the –CH₃– functional group before and after extraction. Ultraviolet spectroscopy further confirms that the lithium ions in the aqueous phase transfer to the organic phase in the form of the LiFeCl₄ complex, indicating that the extracted complex has the structure of LiFeCl₄·3.38TBP·0.72MIBK. Finally, based on recycled materials, a high-performance LiFePO₄/C material is synthesized via a simple solid-phase method, achieving a closed-loop process. This investigation provides new insights and valuable references for the recycling of LFP from spent lithium batteries.