High-value recycling of spent lithium iron phosphate cathode materials

A high-value recycling method was introduced for spent lithium iron phosphate (LFP) cathode materials. Fe, P, and Li elements were recovered in the forms of FeSO₄, FePO₄, and Li₃PO₄, respectively. The recycling yield of Li recovered in the form of Li₃PO₄ reached 93%. The recycling process was free of phosphoric acid and phosphate and involved five steps: ① dissolving the waste lithium iron phosphate cathode material with sulfuric acid; ② recrystallizing more than one-third of Fe²⁺ ions as FeSO₄; ③ oxidizing the remaining Fe²⁺ ions and adjusting the pH value of the solution to 2.0 ~ 3.0 to precipitate Fe²⁺ ions of FePO₄, which can be used for solid-phase preparation of LiFePO₄; ④ adjusting the pH value of the filtrate after separating FePO₄ to 11.0, where the concentrations of Li⁺ ions and PO₄^3- ions met the precipitation conditions to precipitate Li₃PO₄; ⑤ using the obtained ferrous salt and Li₃PO₄ to prepare LiFePO₄ by hydrothermal methods, with the resulting LiFePO₄ exhibiting good electrochemical performance.