O-2-Type Li-2/3[Ni1/3Mn2/3]O-2: A new layered cathode material for rechargeable lithium batteries - II. Structure, composition, and properties

Li-2/3[Ni1/3Mn2/3]O-2 is prepared from the corresponding P2-Na-2/3[Ni1/3Mn2 /3]O-2 by ion exchange. This work investigates the correlation between stru cture, composition, and electrochemical properties. Crystalline Li-2/3[Ni1/ 3Mn2/3]O-2 is a layered oxide with the T2 structure. Small deviations from the Ni1/3Mn2/3 stoichiometry cause less ordered samples showing T2-O2 inter growth structures. Larger deviations (Ni0.25Mn0.75) or doping with 15% Co l ead to stacking-faulted O2 structures instead of T2. Best electrochemical r esults are obtained if the sample has a slightly disordered T2 structure. T he electrochemical properties of O2-Li-2/3[Ni1/3Mn2/3]O-2 are compared to t hose of related phases with the alternative O3 structure. Only O2-type Li-x [Ni1/3Mn2/3]O-2 can be cycled with little loss of capacity as a function of cycle number. (C) 2000 The Electrochemical Society. S0013-4651(99)12-097-4 . All rights reserved.