Fig. 1: Acid-free and selective leaching promoted by mechanical activation.
From: An acid-free process to prepare battery grade nickel and cobalt sulfates from complex resources
a Crystal structure of Ni4.5Fe4.5S8, in which iron (Fe) occupying the tetrahedral or octahedral spaces formed by the closest packing of sulfur (S). b Schematic diagram of the bonding relationships in the Ni sulfide concentrate (NSC) before and after activation, in which the square dotted line frame represents the lattice frame, and the S atoms shaded in purple and green circles represent saturated sulfur (S2-) and undercoordinated sulfur (S1-), respectively. X-ray photoelectron spectroscopy (XPS) data showing the compositional proportions of (c) various sulfur species, d various iron species, and (e) Fe/S in different samples. f S 2p XPS spectra of NSC activated for 0, 20, 60, and 240 min. Leaching efficiency of Ni, Co, Cu and Fe from (g) nonactivated NSC and (h) 240 min activated NSC. The error bars in g, h reflect the standard deviations from three individual experiments. i Flowsheet of the acid-free leaching process, in Route 1, the nonactivated NSC is difficult to leach, while in Route 2, the activated NSC undergoes efficient leaching to obtain a nickel-containing solution, which is ultimately prepared into LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode material. Source data are provided as a Source Data file.
