A new recovery method for fast and efficient selective leaching of lithium from lithium iron phosphate cathode powder is proposed. Lithium is expelled out of the Oliver crystal structure of lithium iron phosphate due to oxidation of Fe${}^{2+}$ into Fe${}^{3+}$ by ammonium persulfate. 99% of lithium is therefore leached at 40 °C with only 1.1 times the amount of ammonium persulfate without the help of acid treatment. The use of ammonium persulfate also avoids the necessity to remove other metal ions in the later purification process. Various characterization methods including SEM, XPS, XRD are used to explore the experimental leaching mechanism. Theoretical investigations are performed which reveals the E-pH diagram of Fe–P–Li–H₂O thermodynamic equilibrium. It confirms the possibility and suggests appropriate pH range allowing direct conversion from lithium iron phosphate to iron phosphate with great energy saving and reduced use of acid and base. Based on the experimental and theoretical results, a green and efficient closed-loop recycling route for lithium iron phosphate is proposed.

提出了一种新的回收方法，用于快速有效地从磷酸铁锂正极粉末中选择性浸出锂。由于铁的氧化，锂从磷酸铁锂的奥利弗晶体结构中排出${}^{\mathrm{2个}+}$ 进入铁${}^{3+}$过硫酸铵。因此，在40°C下仅用过硫酸铵的1.1倍就可以浸出99％的锂，而无需进行酸处理。过硫酸铵的使用还避免了在随后的纯化过程中去除其他金属离子的必要性。SEM，XPS，XRD等多种表征方法被用于探索实验浸出机理。进行了理论研究，揭示了Fe–P–Li–H ₂的E-pH图O热力学平衡。它证实了这种可能性，并提出了合适的pH范围，从而可以从磷酸锂铁直接转化为磷酸铁，同时大大节省了能源，并减少了酸和碱的使用。根据实验和理论结果，提出了绿色高效的磷酸铁锂闭环回收途径。