Berlin 2012 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 30: Functional Materials III

MM 30.5: Vortrag

Mittwoch, 28. März 2012, 11:15–11:30, H 0106

Ultra Fast and Anisotropic Diffusion of Lithium in Silicon Nanostructures — •Stefan Wagesreither, Alois Lugstein, and Emmerich Bertagnolli — Institute for Solid State Electronics, TU-Wien, Vienna, Austria

Silicon based anodes could improve the lithium ion battery technology with a theoretical tenfold higher capacity in comparison to commercially used graphite anodes. Besides the capacity, fast charge and discharge rates and the closely associated diffusion velocity are important aspects of the battery. By improving the diffusion of lithium in silicon, an performance increase of novel silicon anodes for lithium ion batteries could be achieved. Therefore the dependency of lithium diffusion on the crystallographic directions of silicon was investigated with regard to the diffusion velocity. The lithiation of submicron silicon beams isolated on SiO₂ showed an anisotropic behavior with a dependency on the beam direction along the (100) plane. In silicon beams with <110> direction the lithiation was more prolonged than in <100> beams. With an approximation of the Einstein relation L=√(D · t), a diffusion coefficient of D(50^∘C) = 3.36· 10⁻⁷cm²/s was calculated which is 5 orders of magnitude higher than results for bulk silicon at the same temperature. This result is reflected in the formation of lithium silicide dendrites in the favored <110> direction after contact of lithium with a silicon thin film at room temperature.