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 fort-nation of NiO bunsenite and (Ni,Co,Mn)(3)O-4 spinel. (C) 2007 Elsevier B.V. All rights reserved.