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Atomic Scale Account of the Surface Effect on Ionic Transport in Silver Hollandite

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journal contribution
posted on 16.08.2018, 00:00 by Xiaobing Hu, Jianping Huang, Lijun Wu, Merzuk Kaltak, Maria Victoria Fernandez-Serra, Qingping Meng, Lei Wang, Amy C. Marschilok, Esther S. Takeuchi, Kenneth J. Takeuchi, Mark S. Hybertsen, Yimei Zhu
Nanosized electrodes for Li-ion batteries typically display improved electrochemical properties, which are generally attributed to the reduced dimensionality for lithiation. However, the intriguing roles of surface defects and disorder associated with the nanosized materials are often overlooked. Here, combining atomically resolved structural analysis with density functional theory calculations, we reveal that the formation of intrinsic oxygen vacancies near surface in silver hollandite nanorods modifies the local atomic structure and valence state. These surface reconstructions resulted from oxygen vacancies can significantly affect the diffusion pathways in what are otherwise one-dimensional (1D) tunneled structures. On the basis of energy barrier calculations, we demonstrate that the oxygen vacancies boost ionic transport through the edge sharing MnO6 polyhedra in the a–b plane. Thus, within a single rod different from the inherent 1D tunnel diffusion in the interior, the ionic transport at oxygen vacancy decorated surfaces likely adopts a three-dimensional diffusion pathway including both tunnel and planar diffusion.