Improved Lithium Extraction Efficiency by Addition of Diisobutyl Ketone to the Tributyl Phosphate/Iron Trichloride System Obtained From Spent LiFePO ₄ Powder

Abstract In the field of lithium‐ion batteries recycling, the solvent extraction method to recycle valuable elements has been diffusely studied and highlights good application potential. However, the leaching process remains challenged by acidic wastewater generation from inorganic acids or the inefficiency of organic acids, and a single extractant often falls short in achieving optimal extraction efficiency. This study investigates chemical behavior of diisobutyl ketone (DIBK) in the FeCl 3 ‐tributyl phosphate (TBP)‐kerosene lithium extraction system from spent lithium iron phosphate (LiFePO 4 , LFP) powder. The isomorphic substitution method has emerged as an efficient and cost‐effective technology for leaching process, avoiding the generation of acid wastewater. Moreover, results indicate that the first lithium extraction efficiency increases to 84%, representing a 9.4% improvement compared to extractions without DIBK. After two extractions, the overall efficiency reaches 98.9%. DIBK is beneficial to prevent the formation of a third phase by enhancing the solubility of the extracted complex, thereby improving lithium recovery from organic phases. Subsequently, the extracted complex structure is confirmed to be LiFeCl 4 ·1.50TBP·0.27DIBK using the fitting slope method in conjunction with FTIR and UV spectroscopy. Additionally, LiFePO 4 /C is re‐synthesized to achieve closed‐loop processes. This research offers valuable insights and references for the valuable elements recycling.