SKM 2023 – scientific programme
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O: Fachverband Oberflächenphysik
O 59: Electronic Structure of Surfaces I
O 59.10: Talk
Wednesday, March 29, 2023, 17:30–17:45, REC C 213
Exploring polaron stability and defect structures in Li4Ti5O12 (LTO): A combined theoretical and experimental approach — •Yu-Te Chan1, Matthias Kick2, Cristina Grosu2, Christoph Scheurer1, and Harald Oberhofer3 — 1Fritz-Haber-Institut der MPG, Berlin, Germany — 2Massachusetts Institute of Technology, Cambridge, USA — 3University of Bayreuth, Bayreuth, Germany
Spinel Li4Ti5O12 (LTO) is a promising anode material for next-generation all-solid-state Li-ion batteries (ASSB) due to its "zero strain" charge/discharge behavior. Pristine LTO suffers from poor ionic and electronic conductivity. Oxygen vacancies, produced by tailored sintering protocols, yield a performant, blue LTO material. Vacancy induced polarons have been proposed as one of the origins of increased electronic conductivity. However, detailed knowledge about polaron stability, distribution, and dynamics in LTO bulk and surface have been lacking. By performing Hubbard corrected density functional theory (DFT+U) calculations we are able to show that in fact polaron formation and a possible polaron hopping mechanism can not only play a significant role in enhancing electronic conductivity but boost Li+ diffusion nearby, in line with the experimentally observed improved conductivities.[1,2] In combination with positron lifetime spectroscopy data and machine learning models, we arrive at a rather complete picture of the bulk vs. surface defect chemistry in LTO particles and the resulting mixed ionic electronic conductivity. [1] M. Kick et al., J. Phys. Chem. Lett. 11 (2020), 2535 [2] M. Kick et al., ACS Appl. Energy Mater 4 (2021), 8583