A modified ZrO2-coating process to improve electrochemical performance of Li(Ni1/3Co1/3Mn1/3)O2

A modified Zr-coating process was introduced to improve the electrochemical performance of Li(Ni1/3Co1/3Mn1/3)O-2. The ZrO2-coating was carried out on an intermediate, (Ni1/3Co1/3Mn1/3)(OH)(2), rather than on Li(Ni1/3Co1/3Mn1/3)O-2. After a heat treatment process, one part of the Zr covered the surface of Li(Ni1/3Co1/3Mn1/3)O-2 in the form of a Li2ZrO3 coating layer, and the other part diffused into the crystal lattice of Li(Ni1/3Co1/3Mn1/3)O-2. A decreasing gradient distribution in the concentration of Zr was detected from the surface to the bulk of Li(Ni1/3Co1/3Mn1/3)O-2 by X-ray photoelectron spectra (XPS). Electrochemical tests indicated that the 1% (Zr/Ni + Co + Mn) ZrO2-modified Li(Ni1/3Co1/3Mn1/3)O-2 prepared by this process showed better cyclability and rate capability than bare Li(Ni1/3Co1/3Mn1/3)O-2. The result can be ascribed to the special effect of Zr in ZrO2-modified Li(Ni1/3Co1/3Mn1/3)O-2. The Surface coating layer of Li2ZrO3 improved the cycle performance, while the incorporation of Zr in the crystal lattice of Li(Ni1/3Co1/3Mn1/3)O-2 modified the rate capability by increasing the lattice parameters. Electrochemical impedance spectra (EIS) results showed that the increase of charge transfer resistance during cycling was suppressed significantly by ZrO2 modification. (C) 2008 Elsevier B.V. All rights reserved.