| Abstract
| - Electron diffraction revealed evidence of commensurate and incommensurate superstructures in the T#2 phase derived from O2−LiCoO2. It is proposed that lithium and vacancy ordering is the most probable cause for these superstructures. As shown, a 2aorth. × 2borth. × 2corth. superstructure of T#2 is correlated to lithium ordering: there are two variants as two orientations of 8e LiO4 are allowed in T#2; doubling of the corth. parameter results from alternation of these variants along the corth. axis.
- Electron diffraction revealed evidence of commensurate and incommensurate superstructures in an unusual phase, T#2, derived from O2-type layered LiCoO2 upon lithiumdeintercalation. 2aorth. × 2borth. × 2corth., 2aorth. × borth. × corth., and incommensurate with q =(γ = 0.23 and 0.36) superstructures were found. It is believed that lithium andvacancy ordering is the most probable cause for the presence of these superstructures.Lithium ordering configurations were discussed in detail with respect to the superstructuresobserved. It is believed that the presence of various lithium and vacancy orderingconfigurations improves the stability of the T#2 structure over a range of lithium compositions.Nevertheless, it should be mentioned that the nature of superstructures present and possiblelithium ordering configurations in T#2−LixCoO2 were complex and further investigationsare needed. In addition, it is of significance to point out that a combination of transmissionelectron microscopy and electron diffraction showed that three T#2 variants could coexist indifferent regions within one T#2 crystal, which led to the development of a domain (mazed)microstructure.
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