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O: Fachverband Oberflächenphysik
O 49: Poster Session IV: Electronic structure of surfaces: Spectroscopy, surface states II
O 49.3: Poster
Tuesday, March 2, 2021, 13:30–15:30, P
Exploring polaron stability and defect structures in Li4Ti5O12 (LTO) surface: A combined theoretical and experimental approach — •Yu-Te Chan1, Matthias Kick2, Cristina Grosu2,3, Christoph Scheurer1, and Harald Oberhofer2 — 1Fritz Haber Institute — 2TU München — 3IEK-9, FZ Jülich
Spinel Li4Ti5O12 (LTO) is a promising anode material for next-generation all-solid-state Li-ion batteries (ASSB) by its "zero strain" charge/discharge behavior. Pristine, white LTO possesses poor ionic and electronic conductivity. The latter can be increased by tailoring the sintering protocol to produce oxygen vacancies, resulting in a performant, blue LTO material. Polarons induced by oxygen vacancies have been proposed as one of the origins of the high conductivity. Detailed knowledge about polaron stability, distribution, and dynamics in LTO bulk and surface has been lacking, though. 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 play a significant role in the experimentally observed improved conductivities. Moreover we are able to gauge polaronic charge mobility by explicitly calculating polaron hopping barriers.[1,2] In combination with positron lifetime spectroscopy (PALS) data and theoretical positron lifetimes we arrive at a rather complete picture of the bulk vs. surface defect chemistry in LTO particles and their resulting mixed ionic electronic conductivity. [1] M. Kick et al., J. Phys. Chem. Lett. 11 (2020), 2535 [2] M. Kick et al., J. Chem. Phys. 153 (2020), 144701