Structural Stability of LiCoO2 at 400°C

✍ Scribed by Y. Shao-Horn; S.A. Hackney; A.J. Kahaian; M.M. Thackeray

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 536 KB
• Volume: 168
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2002.9679

✦ Synopsis

The relative stability of the lithiated-spinel structure, Li 2 [Co 2 ]O 4 , at 4001C to the layered LiCoO 2 structure has been investigated. ''Low-temperature'' LT-LiCoO 2 samples were synthesized at 4001C by the solid-state reaction of Li 2 CO 3 with CoCO 3 (or Co 3 O 4 ) for various times between 10 min and 232 days. Least-squares refinements of X-ray powder diffraction patterns were used to determine the fractions of lithiated-spinel Li 2 [Co 2 ]O 4 and layered LiCoO 2 in the samples. X-ray powder diffraction and transmission electron microscope data show that Li 2 [Co 2 ]O 4 nucleates from an intermediate Li x Co 1Àx [Co 2 ]O 4 spinel product before transforming very slowly to layered LiCoO 2 . The experimental data confirm the theoretical prediction that layered LiCoO 2 is thermodynamically more stable than the lithiated-spinel structure at 4001C and support the arguments that a non-ideal cation distribution in Li 2 [Co 2 ]O 4 , non-stoichiometry and kinetic factors restrict the transformation of the lithiated-spinel structure to layered LiCoO 2 at this temperature.