Mixed layered Ni–Mn–Co hydroxides: Crystal structure, electronic state of ions, and thermal decomposition

It has been shown that varying conditions of co-precipitation processes, two types of mixed Ni–Mn–Co hydroxides: either brucite, or hydrotalcite-like (LDHs)—with different Ni/Mn/Co ratio can be prepared. According to XPS study, these hydroxides are mixed-valence materials: Ni ions present in 2+ oxidation state, whereas Mn and Co ions are in 3+/4+ and 2+/3+ state, respectively; their oxidation state increases with an increase of their content in hydroxides. For Ni-rich hydroxides, a strong effect of nickel segregation is observed indicating that chemistry of the surface and of the bulk is different. Mixed Ni–Mn–Co hydroxides decompose in two steps resulting in formation of NiO bunsenite and (Ni,Co,Mn)3O4 spinel.