Regensburg 2016 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 12: Frontiers of Electronic Structure Theory: Focus on Topology and Transport
MM 12.2: Talk
Monday, March 7, 2016, 16:00–16:15, H51
Potential-dependent mechanism of Li diffusion in Li2S — •Ashkan Moradabadi1,2 and Payam Kaghazchi1 — 1Institut für Chemie und Biochemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany — 2Institut für Materialwissenschaft, Fachgebiet Materialmodellierung, Technische Universitat Darmstadt, Jovanka-Bontschits-Str. 2, 64287 Darmstadt, Germany
Li-S batteries are promising candidates for large-scale applications such as electrical vehicles. However, the measured discharge capacity is often less than the theoretical one [1,2]. This is mainly due to the slow diffusion of Li through Li2S shells formed on S8 cores, which leads to an incomplete conversion of S8 cores to Li2S (the final product of lithiation of S8). In the present work, using density functional calculation, we have investigated mechanism of Li diffusion in Li2S. At low cell voltages (< 0.93 V), Li diffusion occurs via an exchange mechanism with a high energy barrier of 0.45 eV. However at higher cell voltages, Li diffusion takes place via a vacancy mechanism with a lower energy barrier of 0.27 eV. Our findings can explain the capacity fading in Li-S batteries at high operation rates.
[1] Liang, X.; Hart, C.; Pang, Q.; Garsuch, A.; Weiss, T.; Nazar, L. F.; A highly efficient polysulfide mediator for lithium-sulfur batteries. Nature Communications, 2015, 6, 5682.
[2] Wang, L.; Wang, Y.; Xia, Y.; A high performance lithium-ion sulfur battery based on a Li2S cathode using a dual-phase electrolyte. Energy Environ. Sci. 2015, 8, 1551.