Berlin 2015 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 49: Interfaces I: Structure and Segregation

MM 49.2: Talk

Thursday, March 19, 2015, 10:30–10:45, H 0107

On the origin of anisotropic lithiation of Si — •Ashkan Moradabadi¹, Jochen Rohrer², Karsten Albe², and Payam Kaghazchi¹ — ¹Physikalische und Theoretische Chemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany — ²Institut für Materialwissenschaft, Fachgebiet Materialmodellierung, Technische Universität Darmstadt, Jovanka-Bontschits-Str. 2, 64287 Darmstadt, Germany

Si nanowires (SiNW) are promising candidates for next-generation lithium-ion battery anodes. Lithiation of SiNW anodes proceeds by the movement of interfaces between lithiated amorphous Li_xSi and pristine crystalline Si in a core-shell structure. Experimental studies show that first-cycles of lithiation of SiNWs lead to an anisotropic expansion of SiNWs. In this work, we present density functional theory calculations on Li incorporation in SiNWs using surface and interface geometries. We find that in opposition to the results based on (commonly-used) surface models, the anisotropic expansion of SiNWs does not originate from orientation-dependent barriers for Li diffusion across the Li_xSi/Si interfaces. Due to the disorder nature of interfaces these barriers are distributed isotropically. Instead, here we find that the anisotropic swelling is a consequence of orientation-dependent interface energies and the fact that high-energy interfaces are more mobile than low-energy interfaces.