First-Principles Analysis of Phase Stability in Layered鈥揕ayered Composite Cathodes for Lithium-Ion Batteries

详细信息    查看全文

• 作者：Hakim Iddir ; Roy Benedek
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：April 8, 2014
• 年：2014
• 卷：26
• 期：7
• 页码：2407-2413
• 全文大小：306K
• 年卷期：v.26,no.7(April 8, 2014)
• ISSN：1520-5002

文摘

The atomic order in layered鈥搇ayered composites with composition xLi₂MnO₃路(1 鈥?x)LiCoO₂ is investigated with first-principles calculations at the GGA+U level. This material, and others in its class, are often regarded as solid solutions; however, only a minute solubility of Li₂MnO₃ in a LiCoO₂ host is predicted. Calculations of Co vacancy formation and migration energies in LiCoO₂ are presented to elucidate the rate of vacancy-mediated ordering in the transition-metal-layer. The neutral Co vacancy formation energy is predicted to be in a range centered slightly above 1 eV but varies widely with the oxygen chemical potential. The calculated migration energy for the vacancy with charge q = 鈭?e is approximately 1 eV. These values are small enough to be consistent with rapid ordering in the transition metal layer at typical synthesis temperatures and, therefore, separated Li₂MnO₃ and LiCoO₂ phases. The relatively small (of the order of a few nm) Li₂MnO₃ domain sizes observed with TEM in some xLi₂MnO₃路(1 鈥?x)LiMO₂ composites may result from other factors, such as coherency strain, which perhaps block further domain coarsening in these materials.