Study on impurity removal from black powder of lithium iron phosphate cathode materials†

The recycling of spent LiFePO₄ batteries has garnered significant attention due to its environmental benefits and economic potential. During the practical recycling process, direct crushing and sorting of cathode materials typically produce a black powder containing various metal impurities. The high impurity content in these powders hinders the direct reuse of spent LiFePO₄ cathode materials. This paper presents a novel, simple, and efficient method for impurity removal. The process begins with sieving the black powder obtained from crushed LiFePO₄ cathode materials to effectively separate the cathode active materials from aluminum and copper foils. Alkaline and acid leaching processes are subsequently employed to remove multiple metal impurities, including aluminum, chromium, nickel, and manganese, from the active materials. The resulting leachate is used to prepare battery-grade FePO₄, which is then combined with L_i2CO₃ through a carbothermic reduction process to synthesize LiFePO₄/C. The re-synthesized LiFePO₄/C cathode demonstrates an initial discharge capacity of 155.1 mA h g⁻¹ and retains 96.4% of its electrochemical performance after 100 cycles at a 0.2C rate, meeting the performance requirements for mid-range LiFePO4 batteries. The entire process is eco-friendly and holds significant potential for large-scale recycling of used lithium-ion batteries.