Preparation of high quality layered-layered composite Li2MnO3–LiMO2 (M = Ni, Mn, Co) Li-ion cathodes by a ball milling–annealing process

Abstract

Cathode powders based on the layered-layered composite Li2MnO3–LiMO2 (M=Mn, Co, Ni) have been prepared by a ball milling and annealing process. In principle, this easily scalable and simple process allows for the variation of the stoichiometry, degree of intermixing, and crystallite size by varying the ratio of Li2MnO3 and LiMO2 parent compounds, milling time, and annealing time and temperature. The resultant cathode powder composition of Li1.2Mn0.54Ni0.13Co0.13O2 (M=Mn, Co, Ni) has been shown to have the same crystallographic and electrochemical features as those prepared by conventional sol–gel or co-precipitation methods, with specific discharge capacity of about 250mAhg−1 between 4.7 and 2V. Improvements in specific discharge capacity were demonstrated by the addition of an AlPO4 coating on the cathode powder following the mill-anneal synthesis method. In addition to providing a new means to vary the properties of this cathode system in a more controlled fashion, this synthesis approach also can be used to examine the hypothesis of electrochemical stabilization of the Li2MnO3 by the substitutional LiMO2 structural unit.