Abstract:

K₂S₂O₈ was used as an oxidant to treat the cathode powder of spent lithium iron phosphate (LiFePO₄) 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 Li₃PO₄ precipitation by adding K₃PO₄. 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.

Key words: spent lithium iron phosphate batteries, recovery, mechanical solid-phase oxidation, leaching, selectivity, potassium persulfate

摘要：

采用K₂S₂O₈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（LiFePO₄）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K₃PO₄将浸出的锂离子以Li₃PO₄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LiFePO₄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。

关键词: 废旧磷酸铁锂电池, 回收, 机械固相氧化, 浸取, 选择性, 过硫酸钾