Layered LiCoO2 with a different oxygen stacking (O-2 structure) as a cathode material for rechargeable lithium batteries

O2-LiCoO2 was prepared from Na2/3CoO2 by ion exchange in LiBr dissolved in hexanol. The structure of O2-LiCoO2 was investigated by X-ray diffraction a nd in situ X-ray diffraction during electrochemical charging. The possibili ty of application as cathode materials in rechargeable lithium batteries wa s investigated. Wr find that the electrochemical properties of O2-LiCoO2 as cathodes in lithium batteries are competitive with "conventional: O3-LiCoO 2. During cycling, the O2 structure of LiCoO2 remains stable and does not c onvert to the thermodynamically stable O3-LiCoO2. Both O2 and O3-LixCoO2 sh ow a strong feature in their differential capacity vs. voltage at x near on e-half. which is probably caused by the ordering of Li atoms within each la yer, suggesting that this is not strongly perturbed by the details of the s tacking of the "CoO2" sheets. Finally. the reactivity of O2-LixCoO2 with el ectrolyte was studied by differential scanning coulometry of charged cathod es and compared to that of conventional O3-LixCoO2. O2-LiCoO2 shows similar reactivity. (C) 2000 The Electrochemical Society. S0013-4651(99)07-021-4. All rights reserved.