Hydrometallurgical Synthesis of Nickel Nano-Sulfides from Spent Lithium-Ion Batteries

By developing technologies, spent lithium-ion batteries (LIBs) are considered a great source of nickel-cobalt ions to fabricate metal sulfide nanoparticles. However, the presence of unnecessary ions such as manganese and lithium may hamper the formation of pure metal sulfide nanostructures where the utilization of proper ligand(s) can be very critical. For this reason, the present study initially introduces a promising and cost-effective acidic leaching followed by precipitation and thermal treatment (~250 °C, 1 h) processes to fabricate pure NiS nanopowders from the LIBs, while considering potassium amyl xanthate as the precipitating agent. The produced nanoparticle’s size and structure were characterized by commonly used and advanced analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photon correlation spectroscopy (PCS), and inductively coupled plasma optical emission spectrometry (ICP-OES). The elemental distributions and functional groups were analyzed through energy dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR) methods. The characteristic analyses of the spherical-like NiS particles showed a mean particle size of 61 ± 2 nm (by TEM) and 64 nm (through the PCS method) with high purities approved via XRD and EDS analyses. Moreover, comparing the obtained XRD data with the standard ones showed a perfect match with the hexagonal structure of the NiS phase. We finally concluded that such a presented approach is very practical and efficient for converting the LIBs to an extremely valuable product. Future studies are suggested for the fundamental conceptualization of the processes.