Effect of electronic state of ions on the electrochemical properties of layered cathode materials LiNi1−2x Co x Mn x O2

The cathode materials of the composition LiNi1 − 2x Co x Mn x O2 (x = 0.1, 0.2. 0.33) synthesized from the Ni, Co, Mn mixed hydroxides and LiOH by using mechanical activation method are studied. It is shown that all synthesized compounds have layered structure described by the space group R-3m. With the decreasing of the nickel content the cell volume and the degree of structure disordering decrease. According to XPS data, the electronic main state of d-ions at the prepared samples’ surfaces corresponds to Ni2+, Co3+, and Mn4+. An increase in the nickel content leads to the increase of the Ni2p 3/2 and Co2p 3/2 binding energy, which points to the change in the Me-O bond covalence. According to magnetic susceptibility measurements data, the nickel ions in LiNi0.6Co0.2Mn0.2O2 exist in the two oxidation states: Ni2+ and Ni3+. It is shown that this sample has the highest specific discharge capacity (∼170 mAh/g). The positions of redox peaks in the differential capacitance curves depend on the sample composition: with the increasing of nickel content they are shifted toward lower voltages.