Regeneration of battery-grade iron phosphate from lithium extraction slag of spent lithium iron phosphate cathode material
In addressing the complexities inherent in the current recycling process of waste lithium iron phosphate(LiFePO4)battery cathode materials,characterized by selective lithium extraction,leaving behind a lithium extraction slag with limited utility due to challenges associated with aluminum impurity separation,this study proposed a wet process based on"copper powder-enhanced sulfuric acid leaching-iron powder replacement-selective aluminum separation"strategy to regenerate iron phosphate from the lithium extraction slag.The study involved the optimization and kinetic analysis of the copper powder-enhanced sulfuric acid leaching,focusing on the impacts of parameters such as copper powder dosage,sulfuric acid dosage,liquid-solid ratio,reaction temperature,and reaction time.In addition,the optimization parameters governing the iron powder replacement process for copper retrieval and selective aluminum separation were delineated.The results indicated that the sulfuric acid leaching process of lithium extraction slag were enhanced by copper reduction conformed to the mixed diffusion control model,with an apparent activation energy of 37.12 kJ·mol-1.This indicated that the process was controlled by diffusion through the boundary layer of the solution and the chemical reaction at the interface.Moreover,the concentrations of copper and aluminum in the purified solution were lower than 1 and 41 mg·L-1,respectively,making it suitable for deployment in the synthesis of battery-grade iron phosphate.This study provides a novel approach for the recycling and utilization of lithium extraction slag.
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