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Kinetic Monte Carlo Study of Ambipolar Lithium Ion and Electron–Polaron Diffusion into Nanostructured TiO2

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journal contribution
posted on 16.12.2015, 21:40 by Jianguo Yu, Maria L. Sushko, Sebastien Kerisit, Kevin M. Rosso, Jun Liu
Nanostructured titania (TiO2) polymorphs have proved to be promising electrode materials for next-generation lithium ion batteries. However, there is still a lack of understanding of the fundamental microscopic processes that control charge transport in these materials. Here, we present microscopic simulations of the collective dynamics of lithium ion (Li+) and charge-compensating electron–polarons (e) in rutile TiO2 nanoparticles in contact with an idealized conductive matrix and electrolyte. Kinetic Monte Carlo simulations are used, parametrized by molecular-dynamics-based predictions of activation energy barriers for Li+ and e diffusion. Simulations reveal the central role of electrostatic coupling between Li+ and e on their collective drift diffusion at the nanoscale. They also demonstrate that a high contact area between the conductive matrix and rutile nanoparticles leads to undesirable coupling-induced surface saturation effects during Li+ insertion, which limits the overall capacity and conductivity of the material. These results help provide guidelines for design of nanostructured electrode materials with improved electrochemical performance.