O2 structure Li-2/3[Ni1/3Mn2/3]O-2: A new layered cathode material for rechargeable lithium batteries III. Ion exchange

The ion exchange of Li for Na in P2-structure Na-2/3[Ni1/3Mn2/3]O-2 to make T2-structure Li-2/3[Ni1/3Mn2/3]O-2 is studied. Electron micrographs show t hat the hexagonal plate-like crystal habit is preserved during ion exchange . Ion exchange is successful and equivalent using both molten salts and con centrated Li+-containing aqueous solutions. By controlling the Li:Na ratio in the ion exchange, it is possible to prepare an intermediate phase of app roximate composition Li1/3Na1/3[Ni1/3Mn2/3]O-2, where filled alkali layers of Li and Na alternate, thus doubling the c axis of the material. A summary of ion-exchange reactions of Li for Na in other layered Na-bronzes, such a s P3-Na-2/3[Ni1/3Mn2/3]O-2, O3-Na[Ni1/2Mn1/2]O-2, P2-Na-2/3[CoxMn1-x]O-2, P 3-Na-2/3[CoxMn1-x]O-2, P2-Na2/3CoO2, P2-Na-2/3[Fe1/3Mn2/3]O-2, P2-Na-2/3[Fe 2/3Mn1/3]O-2, P2-Na-2/3[Mg1/3Mn2/3]O-2. P2-Na-2/3[Ni1/3Mn2/3]O-2, and O3-Na MnO2, is given. (C) 2000 The Electrochemical Society. S0013-4651(99)12-108- 6. All rights reserved.