废旧磷酸铁锂电池机械化学固相氧化回收锂机理

Mechanism study on mechanochemical solid-phase oxidation recovery of spent Li_(3)PO_(4) batteries

采用K_(2)S_(2)O_(8)作为氧化剂,分别通过氧化浸出、机械活化联合氧化浸出、机械固相氧化联合水浸三种方法对废旧磷酸铁锂(LiFePO_(4))电池正极粉末进行处理。结果表明,在三种方式最优条件下,氧化浸出方式的Li浸出率为89.03%(质量分数)、机械活化联合氧化浸出方式的Li浸出率为92.36%(质量分数),机械固相氧化联合水浸方式的效果最佳,Li浸出率为98.26%(质量分数),此时Fe化合物与Li完全分离,选择性较高。通过添加K_(3)PO_(4)将浸出的锂离子以Li_(3)PO_(4)沉淀的形式提取回收,经电感耦合等离子体质谱仪检测,纯度可达98.67%(质量分数)。X射线衍射和X射线光电子能谱分析浸出机理,结果表明,在机械化学固相氧化过程中,机械力不仅诱导了LiFePO_(4)粒度的减小,还作为氧化反应的驱动力,使得Li^(+)迁出,Fe(Ⅱ)被氧化为Fe(Ⅲ),为之后的水浸过程提供了良好条件,实现了Li和Fe的选择性分离。

K_(2)S_(2)O_(8) was used as an oxidant to treat the cathode powder of spent lithium iron phosphate(LiFePO_(4))batteries by three methods:oxidation leaching,mechanical activation combined oxidation leaching,and mechanical solid-phase oxidation combined water leaching.The results showed that under the optimal conditions of the three methods,the Li leaching rate of the oxidation leaching method was 89.03%(mass),and the Li leaching rate of the mechanical activation combined oxidation leaching method was 92.36%(mass).The mechanical solid-phase oxidation combined with water leaching method had the best effect,with a Li leaching rate of 98.26%(mass).At this point,Fe compounds can also be completely separated from Li,improving selectivity.The leached lithium ions were extracted and recovered in the form of Li_(3)PO_(4) precipitation by adding K_(3)PO_(4).After detection by inductively coupled plasma mass spectrometry,the purity can reach 98.67%(mass).The leaching mechanism was analyzed by using X-ray diffraction and X-ray photoelectron spectroscopy.The results showed that in the process of mechanochemical solid-phase oxidation,mechanical force not only induced a decrease in particle size,but also acted as a driving force for the oxidation reaction,causing Li^(+)to migrate out and Fe(Ⅱ)to be oxidized to Fe(Ⅲ),providing good conditions for the subsequent water leaching process and achieving selective separation of Li and Fe.