Efficient recovery of valuable metals from spent Lithium-ion batteries by pyrite method with hydrometallurgy process

With the generation of a large number of spent lithium-ion batteries (LIBs), a large amount of valuable metals in spent LIBs is in urgent need of recovery for resource recycling and environmental protection. In the hydrometallurgy recycling process of cathode materials, reducing agents are essential, while traditional ones suffer from high dosage, high price and environmental unfriendliness. Herein, pyrite (FeS₂) is developed as an alternative to achieve efficient recovery of valuable metals. Leaching parameters such as sulphuric acid concentration, liquid/solid ratio, FeS₂ dosage, temperature, and leaching duration were systematically optimized to obtain 98 %∼99.9 % leaching efficiencies of Ni, Co, Mn, and Li from spent LIBs. Thermodynamically, the entire leaching process is feasible. Kinetic studies have shown that the reaction activation energies for Ni, Co, Mn, and Li are in the range of 20 kJ mol⁻¹ to 30 kJ mol⁻¹, implying that the limiting step of the reaction is the diffusion process. Apart from this, the present work provides that the Fe and S in pyrite play a synergistic role in the reduction process based on the application of XRD, SEM, XPS, redox potential testing, ICP and other detection methods. The entire process greatly reduces the involvement of chemical reagents, achieves efficient leaching of valuable metals by the pioneering pyrite method, and compliance with environment-friendly regulations as much as possible.