Layered (1-x-y)LiNi(1/2)Mn(1/2)O(2) [center dot] xLi[Li(1/3)Mn(2/3)] O(2) [center dot] yLiCoO(2) (0<=x = y<=0.3 and x+y=0.5) cathode materials

An exploration of new cathode materials along the two lines having the nominal compositions of (1 - x - y)LiNi1/2Mn1/2O2.xLi[Li1/3Mn2/3]O-2.yLiCoO(2) (0 less than or equal to x = y less than or equal to 0.3 and x + y = 0.5) was performed in the phase diagram of LiNi1/2Mn1/2O2-Li[Li1/3Mn2 3]O-2-LiCoO2 by a simple solid-state reaction. XRD results identified that all materials are pure phases with layered structure, indicating good structural compatibility between three layered compounds, LiNi1/2Mn1/2O2, Li[Li1/3Mn2/3]O-2, and LiCoO2. Li[Li1/3Mn2/3]O-2 and LiCoO2 contents in these electrode materials presented important effects on structure and electrochemical properties. Our results demonstrated that the suitable structural integration of Li[Li1/3Mn2/3]O-2 and LiCoO2 components into LiNi1/2Mn1/2O2 structure is a practicable way to prepare new electrode materials with the desired electrochemical performances even via a simple solid-state reaction. Among the materials investigated in this work, a reversible capacity of 180-200 mAh/g was obtained for the materials with 0.3 less than or equal to x + y less than or equal to 0.6 and excellent cycling performance was observed with a large x (x greater than or equal to 0.25) value in the series of x + y = 0.5. (C) 2004 The Electrochemical Society