Study on Impurity Removal from Black Powder of Lithium Iron Phosphate Cathode Materials

Abstract

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 Li2CO3 through a carbothermic reduction process to synthesize LiFePO4/C. The re-synthesized LiFePO4/C cathode demonstrates an initial discharge capacity of 155.1 mAh/g and retains 96.4% of its electrochemical performance after 100 cycles at a 0.2 C rate, meeting the performance requirements for mid-range LiFePO4 batteries. The entire process is environmentally friendly and shows great promise for industrial-scale recycling of end-of-life lithium-ion batteries.