LiNi1 − x − y Co x Mn y O2 (x = y = 0.1, 0.2, 0.33) cathode materials prepared using mechanical activation: Structure, state of ions, and electrochemical performance

Abstract

We have investigated LiNi1 − x − y Co x Mn y O2 (x = y = 0.1, 0.2, 0.33) cathode materials synthesized from mechanically activated mixtures of lithium hydroxide and nickel cobalt manganese hydroxide. The materials have a layered structure (sp. gr. $$R\bar 3m$$ ). Their unit-cell volume and the degree of disordering in their structure decrease with decreasing nickel content. According to x-ray photoelectron spectroscopy data, the major states of the transition-metal ions in the surface layer of the materials are Ni2+, Co3+, and Mn4+. With increasing nickel content, the Ni 2p 3/2 and Co 2p 3/2 binding energies increase, attesting to changes in M-O bond covalence. The highest specific electrochemical capacity, ∼170 mA h/g, is offered by LiNi0.6Co0.2Mn0.2O2. The position of redox peaks in the differential capacity curves of the three materials depends on composition: with increasing nickel content, the peaks shift to lower voltages.