Regensburg 2022 – scientific programme
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O: Fachverband Oberflächenphysik
O 82: Electronic Structure of Surfaces 2
O 82.2: Talk
Friday, September 9, 2022, 10:45–11:00, S053
Exploring polaron stability and defect structures at the Li4Ti5O12 (LTO) surface: A combined theoretical and experimental approach — •Yu-Te Chan1, Matthias Kick2, Cristina Grosu2,3, Christoph Scheurer1, and Harald Oberhofer2 — 1Fritz-Haber-Institut — 2TU München — 3IEK-9, FZ Jülich
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, white LTO possesses poor ionic and electronic conductivity. Through tailoring the sintering protocol, one can 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 higher electronic conductivity. However, detailed knowledge about polaron stability, distribution, and dynamics in LTO bulk and surface has 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 through lowering the hopping barrier, in line with the experimentally observed improved conductivities.[1,2] In combination with positron lifetime spectroscopy data and theoretical positron lifetimes, 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