Optimization of Ni2+/Ni3+ ratio in layered Li(Ni,Mn,Co)O2 cathodes for better electrochemistry

A study of the LiNi1-x-yCoxMnyO2 (x=y=0-1; 0.2; 0.33) cathode materials prepared from mixed hydroxides and LiOH using the method of mechanical activation has been performed. All as prepared materials were indexed in the R-3m space group. The cell volume and the degree of structural disordering decrease with reducing of Ni content. According to XPS study, the main electronic state of d-ions in the surface layer of particles corresponds to Ni2+, Co3+ and Mn4+. However, the Ni2P(3/2) and Co2P(3/2) binding energy increases versus Ni content, indicating the increased Me-O bond covalency. The highest specific discharge capacity was observed for LiNi0.6Co0.2Mn0.2O2-170 mAh g(-1). The position of redox peaks on the differential capacity curves depends on the composition of the sample: it shifts towards lower voltage with increased Ni content. (c) 2007 Elsevier B.V All rights reserved.