机械化学活化对磷酸铁锂电池中锂选择性浸出特性的影响

针对传统方法不能实现废旧磷酸铁锂电池正极材料(LiFePO₄)中锂(Li)选择性回收的问题，研究了“机械化学活化+浸出”联合工艺对Li选择性浸出的效果。对机械化学活化和浸出的工艺参数进行优化后，确定机械化学活化阶段的优化条件为：药剂用量(NH₄)₂SO₄: LiFePO₄摩尔比为1∶1、球料比为10∶1、湿磨时间为30 min。浸出阶段的优化条件为：浸出温度为80 ℃、H₂O₂体积分数为4%、固液比为50∶1 (g∶L)，浸出时间为50 min。浸出反应的机理为，机械活化后，LiFePO₄的晶格发生错位，颗粒粒径减小；浸出后LiFePO₄中Fe的价态发生变化、Li与共磨剂络合。在优化的条件下，Li的浸出率为99.55%、Fe的浸出率为0，达到了选择性浸出Li的目的。本研究所开发的机械化学活化法可为高选择性回收废旧锂电池中的Li提供参考。

Effect of mechanochemical activation on the selective leaching properties of lithium from LiFePO4 batteries

In order to overcome the drawback of traditional recycling methods that can not selectively recover lithium (Li) from waste LiFePO4 cathode material, the performance of the mechanochemical activation and leaching joint process on the selective leaching of Li was studied. After optimizing the parameters of mechanochemical activation and leaching, the optimum conditions of mechanochemical activation stage were determined as follows: (NH4)2SO4∶LiFePO4 molar ratio of 1∶1, ball and materials ratio of 10∶1 and wet grinding time of 30 min; and the optimum conditions of leaching stage were determined as follows: leaching temperature of 80 ℃, 4%(volume ratio) H2O2, solid-liquid ratio of 50∶1 (g∶L) and leaching time of 50 min. The mechanisms of leaching reaction could be illustrated as follows. After mechanical activation, the dislocation of LiFePO4 lattice and the reduction of particle size occurred. Meanwhile the change of valence state of Fe in LiFePO4 and the complexation between Li and abrasives appeared during leaching process. Under the optimized conditions, the leaching rate of Li was 99.55% and the leaching rate of Fe was 0, thus the selective recovery of Li was achieved. The environmentally friendly mechanochemical activation method developed in this study could provide technical supports for the recovery of precious metals in waste lithium batteries with high selectivity