Layered LiCoO[sub 2] with a Different Oxygen Stacking (O2 Structure) as a Cathode Material for Rechargeable Lithium Batteries

Abstract

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 and in situ X-ray diffraction during electrochemical charging. The possibility of application as cathode materials in rechargeable lithium batteries was investigated. We find that the electrochemical properties of O2-LiCoO2 as cathodes in lithium batteries are competitive with 'conventional: O3-LiCoO2. During cycling, the O2 structure of LiCoO2 remains stable and does not convert to the thermodynamically stable O3-LiCoO2. Both O2 and O3-LixCoO2 show a strong feature in their differential capacity vs. voltage at x near one-half, which is probably caused by the ordering of Li atoms within each layer, suggesting that this is not strongly perturbed by the details of the stacking of the 'CoO2' sheets. Finally, the reactivity of O2-LixCoO2 with electrolyte was studied by differential scanning coulometry of charged cathodes and compared to that of conventional O3-LixCoO2. O2-LiCoO2 shows similar reactivity.