Role of chemical and structural stabilities on the electrochemical properties of layered LiNi1/3Mn1/3Co1/3O2 cathodes

With an aim to develop an understanding of the higher reversible capacities exhibited by the layered LiNi1/3Mn1/3Co1/3O2 cathode compared to that of LiCoO2, its chemical and structural stabilities are investigated by characterizing the samples obtained by chemical lithium extraction. The LiNi1/3Mn1/3Co1/3O2 cathode prepared by firing the coprecipitated hydroxides of the transition metal ions with 7 atom % excess lithium hydroxide exhibits a discharge capacity of 180 mAh/g (at 4.6-3.0 V and C/5 rate) with 90% capacity retention in 50 cycles. The higher reversible capacity of LiNi1/3Mn1/3Co1/3O2 is attributed to its better chemical and structural stability down to a lower lithium content of (1 - x) approximate to 0.35 compared to (1 - x) approximate to 0.5 with the analogous Li1-xCoO2 cathode. The Li1-xNi1/3Mn1/3Co1/3O2 system is found to be chemically stable for (1 - x) approximate to 0.35 without tending to lose any oxygen from the lattice and structurally stable for at least (1 - x) approximate to 0.23 by maintaining the initial O-3 structure. (c) 2005 The Electrochemical Society.