Improved electrochemical performance of layered LiNi0.4Co0.2Mn0.4O2 via Li2ZrO3 coating

A Li2ZrO3 coating technique was successfully applied to layered lithium transition metal mixed oxide LiNi0.4Co0.2Mn0.4O2 to enhance its electrochemical performance using Zr(NO3)(4)center dot 5H(2)O and CH3COOLi center dot 2H(2)O as coating reagents. The existence of Li2ZrO3 coating layer was identified by X-ray diffraction (XRD), Environmental scanning electron microscopy (ESEM), Transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The Li2ZrO3 shell decreased the exposed area of electrode core to electrolyte, and thus suppressed the dissolution of transition metal and side reaction between them. In addition, coating with Li2ZrO3 improved the ion transportation characteristics. As a result, an enhanced electrochemical performance in terms of discharge capacity, rate performance, and capacity retention were obtained, especially at higher temperature of 50 degrees C. Analysis of electrochemical impedance spectra (EIS) showed that the coated material exhibited lower charge transfer resistance (R-ct) with less variation during cycling, which indicated the electrode/electrolyte interface of coated material was more favorable and stable for electrochemical reaction. (C) 2007 Elsevier Ltd. All rights reserved.