Shell Model for Atomistic Simulation of Lithium Diffusion in Mixed Mn/Ti Oxides

详细信息    查看全文

• 作者：Sebastien Kerisit ; Anne M. Chaka ; Timothy C. Droubay ; Eugene S. Ilton
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：October 23, 2014
• 年：2014
• 卷：118
• 期：42
• 页码：24231-24239
• 全文大小：432K
• ISSN：1932-7455

文摘

Mixed Mn/Ti oxides present attractive physicochemical properties such as their ability to accommodate Li for application in Li-ion batteries. In this work, atomic parameters for Mn were developed to extend an existing shell model of the Li鈥揟i鈥揙 system and allow simulations of pure and lithiated Mn and mixed Mn/Ti oxide polymorphs. The shell model yielded good agreement with experimentally derived structures (i.e., lattice parameters and interatomic distances) and represented an improvement over existing potential models. The shell model was employed in molecular dynamics (MD) simulations of Li diffusion in the 1 脳 1 c-direction channels of Li_xMn_1鈥?i>yTi_yO₂ with the rutile structure, where 0 鈮?x 鈮?0.25 and 0 鈮?y 鈮?1. In the infinite dilution limit, the arrangement of Mn and Ti ions in the lattice was found to have a significant effect on the activation energy for Li diffusion in the c channels due to the destabilization of half of the interstitial octahedral sites. Anomalous diffusion was demonstrated for Li concentrations as low as x = 0.125, with a single Li ion positioned in every other c channel. Further increase in Li concentration showed not only the substantial effect of Li鈥揕i repulsive interactions on Li mobility but also their influence on the time dependence of Li diffusion. The results of the MD simulations can inform intrinsic structure鈥損roperty relationships for the rational design of improved electrode materials for Li-ion batteries.