Morphologies and electrochemical properties of 0.6Li2MnO3·0.4LiCoO2 composite cathode powders prepared by spray pyrolysis

Abstract

Nanosized 0.6Li2MnO3·0.4LiCoO2 composite cathode powders are prepared by spray pyrolysis. The micron-sized composite powders are converted into nanosized powders by a simple milling process. The mean sizes of the composite powders measured from the TEM images increase from 20 to 170 nm when the post-treatment temperatures increase from 650 to 900 °C. The Brunauer–Emmett–Teller surface areas of the composite powders post-treated at 650 and 900 °C are 24 and 3 m2 g−1, respectively. The XRD patterns indicate that the layered composite powders post-treated at 800 and 900 °C have high crystallinity and low cation mixing. The mean crystallite sizes of the powders, measured from the (003) peak widths of the XRD patterns using Scherrer's equation, are 35 and 56 nm at post-treatment temperatures of 800 and 900 °C, respectively. The initial discharge capacities of the 0.6Li2MnO3·0.4LiCoO2 composite are 262, 267, 264, and 263 mAh g−1 when the post-treat temperatures of the powders are 650, 700, 800, and 900 °C, respectively. The discharge capacity of the composite powders post-treated at 900 °C abruptly decreases from 263 to 214 mAh g−1 by the seventh cycle and then slowly decreases to 198 mAh g−1 with increasing cycle number, up to 30.