Application of Mechanical Activation for the Synthesis of Cathode Materials Based on Solid Solutions LiNi1-yCoyO2
N. V. Kosova, E. T. Devyatkina, A. B. Slobodyuk
Keywords: mechanical activation, lithium ion rechargeable batteries, cathode materials, LiNi1-yCoyO2, Li MAS NMR, cycling
Pages: 141-149
Abstract
Dry, waste-free and energy-saving synthesis of cathode materials for lithium ion rechargeable batteries based on solid solutions of the composition LiNi1-yCoyO2 (y = 0.2, 0.4, 0.6, 0.8) was carried out. Double hydroxides of nickel and cobalt, as well as anhydrous oxides of nickel and cobalt in mixture with lithium hydroxide were used as the initial reagents. It was shown that, independently of the initial reagents, the samples are characterized by high dispersity, phase uniformity and are indexed in the space group R3m. With an increase in nickel content, lattice parameters а and с increase; a good correspondence with Wegard rule for solid solutions in the system LiNiO2-LiCoO2 is observed. The bands in the IR spectrum shift to smaller frequencies as a result of a decrease in covalence in the layer (Ni1-yCoyO2)2. The 6,7Li NMR spectra contain two components which are shifted both to the positive and to the negative region and provide evidence of the interaction of lithium ions with Ni3+ ions in the first and the second coordination spheres. Analysis of the fine structure of the second component of MAS spectra situated near 0 ppm showed that nickel ions in the layers Ni1-yCoyO2 are distributed non-uniformly for 0.6 ≤ (1-y) ≤ 0.8. Such a deviation from the random distribution of Ni/Co has a narrow local character and is not detected by means of XPA but affects the electrochemical properties of cathode materials.
|
