Structure, Size, and Morphology Control of Nanocrystalline Lithium Cobalt Oxide

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• 作者：Kirsten M. 脴. Jensen ; Mogens Christensen ; Christoffer Tyrsted ; Martin Bremholm ; Bo B. Iversen
• 刊名：Crystal Growth & Design
• 出版年：2011
• 出版时间：March 2, 2011
• 年：2011
• 卷：11
• 期：3
• 页码：753-758
• 全文大小：926K
• 年卷期：v.11,no.3(March 2, 2011)
• ISSN：1528-7505

文摘

Hydrothermal synthesis of nanocrystalline LiCoO₂ from CoOOH and LiOH is studied by in situ powder X-ray diffraction. The study confirms that transformation from CoOOH to LiCoO₂ takes place through a dissolution鈭抮ecrystallization process, where the dissolution step is rate determining. Therefore, a high solubility of CoOOH is needed to ensure a fast reaction, and this can be achieved by increasing the temperature or the pH value. The growth rates and the final sizes of the LiCoO₂ nanoparticles are observed to be highly dependent on the synthesis temperature. The nanoparticles are disk shaped, and the in situ data show that the degree of anisotropy in the morphology is temperature dependent. Thus, not only particle size but also morphology is controllable. The in situ data also show that at low temperature and low LiOH concentration, the Fd3m polymorph of LiCoO₂ is first crystallized, but sustained reaction leads to a transformation to the R3̅m polymorph. At other conditions the R3̅m polymorph forms directly within the time resolution (10 s). Finally, the unit cell is observed to change significantly with particle size. However, at low LiOH concentrations peculiar anisotropic unit cell changes are observed, which cannot be explained by particle size effects or Li defects.