三元正极材料废粉氢还原-水浸提锂过程典型杂质的影响

对含杂三元正极废粉和纯三元正极粉进行了氢还原-水浸提锂工艺对比试验,采用XRD、SEM-EDS和红外光谱等检测手段对反应产物进行表征分析。结果表明,纯三元正极粉较佳焙烧条件为: 焙烧温度500 ℃、焙烧时间30 min、氢气流量100 mL/min,此条件下所得焙烧料在浸出液固比10∶1、温度90 ℃、时间120 min条件下浸出,锂浸出率为98.71%。含杂三元正极废粉较佳焙烧条件为: 焙烧温度500 ℃、焙烧时间90 min、氢气流量100 mL/min,此条件下所得焙烧料在相同条件下水浸时,锂浸出率为84.74%。含杂三元正极废粉锂浸出率明显低于纯三元正极粉,原因是含杂三元正极废粉中存在F、P、Al等杂质,在还原焙烧过程中部分锂与杂质成分反应,生成水溶性差的LiF、Li3PO4和LiAlO2,进而降低了锂浸出率。

Effect of Typical Impurities on Recovery of Lithium from Spent NCM Cathode Powder with Hydrogen Reduction Roasting and Water Leaching Process

The spent NCM cathode powder with or without impurities was taken for a comparative experiment to be treated with a combined process of hydrogen reduction roasting and water leaching, and the obtained corresponding products were then characterized by using XRD, SEM-EDS and infrared spectroscopy. It is found that the leaching rate of lithium can reach 98.71%, after the NCM cathode powder without impurities is optimally roasted at 500 ℃ for 30 min with hydrogen flow at 100 mL/min and the obtained roasted product is then leached at 90 ℃ for 30 min with liquid-solid ratio at 10∶1. But the leaching rate of lithium is 84.74%, after the NCM cathode powder with impurities optimally roasted at 500 ℃ for 90 min with hydrogen flow at 100 mL/min and the obtained roasted product is then water leached at the same conditions. It is shown that the leaching rate of lithium from NCM cathode powder with impurities is obviously lower than that from NCM cathode powder without impurities, due to the existence of impurities of F, P and Al, which react with part of Li during the reduction roasting process, generating LiF, Li₃PO₄ and LiAlO₂ with poor water solubility, thus reducing the lithium leaching rate.