废旧磷酸铁锂正极材料提锂渣再生电池级磷酸铁

Regeneration of battery-grade iron phosphate from lithium extraction slag of spent lithium iron phosphate cathode material

针对目前废旧磷酸铁锂电池正极材料回收中仅局限于高经济价值的锂元素提取,由于铝杂质分离困难而导致提锂渣利用率低的问题,提出了一种基于“铜粉强化硫酸浸出-铁粉置换-选择性分铝”策略的湿法工艺,旨在从提锂渣中高效再生磷酸铁。通过对铜粉强化硫酸过程进行优化及动力学研究,着重考察了铜粉用量、硫酸用量、液固比、反应温度及反应时间等参数的影响,确定了铁粉置换回收铜和选择性分铝过程的相关优化参数。研究结果表明,铜粉强化提锂渣硫酸浸出过程符合混合扩散控制模型,其表观活化能为37.12 k J·mol^(-1),主要受溶液边界层的扩散和界面处的化学反应共同控制。此外,经过净化处理后,溶液中铜和铝的浓度分别降至小于1、41 mg·L^(-1),可直接用于电池级磷酸铁的制备。本研究为磷酸铁锂提锂渣的回收利用提供了一种新思路。

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 batterygrade iron phosphate.This study provides a novel approach for the recycling and utilization of lithium extraction slag.