X-ray diffraction study on LixCoO2 below ambient temperature

✍ Scribed by K. Mukai; H. Nozaki; Y. Ikedo; J. Sugiyama; K. Ariyoshi; T. Ohzuku

• Book ID: 104025637
• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 850 KB
• Volume: 192
• Category: Article
• ISSN: 0378-7753
• DOI: 10.1016/j.jpowsour.2009.03.004

✦ Synopsis

In order to elucidate the structural change of Li x CoO 2 with temperature (T), powder X-ray diffraction measurements have been carried out using a synchrotron radiation source in the T range between 300 and 90 K for the samples with x = 1.02, 0.60, 0.56, and 0.53. The samples with x < 1.02 were prepared by an electrochemical reaction in a non-aqueous lithium cell. The x = 1.02 and 0.60 samples are in a rhombohedral phase (R 3m) in the whole T range measured. On the other hand, the x = 0.56 and 0.53 samples exhibit a structural transition around 140 K, although the both samples are in a monoclinic phase (C2/m) down to 90 K. That is, the angle between a M -and c M -axis (ˇM) increases monotonically down to 150 K, then increases more rapidly with further lowering T. The values of ˇand a M /b M , which are parameters to characterize a monoclinic distortion from the hexagonal symmetry, are ˇ> +0.6 • and a M /b M < 1.732 above 140 K, while ˇ< +0.6 • and a M /b M ≈ 1.732 below 140 K. This suggests that the monoclinic distortion below 140 K is mainly caused by a gliding along the basal plane.