Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 67: SYLI: Symposium Interfacial Challenges in Solid-State Li Ion Batteries - defects, structure and thermodynamics

O 67.4: Vortrag

Mittwoch, 22. März 2017, 11:00–11:15, IFW A

Modeling occupational disorder in Li4Ti5O12 battery materials: Intrinsic complexity and its effect on ion mobility — •Hendrik H. Heenen, Christoph Scheurer, and Karsten Reuter — Technische Universität München, Germany

Lithium-titanium-oxide (Li4Ti5O12, LTO) is unique among battery materials due to its exceptional cyclability and high rate capability. This performance is assumed to derive at least partly from the occupational disorder introduced via mixed Li/Ti occupancy in the LTO spinel-like structure. Notwithstanding, the exact atomic-scale influence of this disorder on Li ion mobility remains an open question.

We explore the vast configuration space accessible during high-temperature LTO synthesis by Wang-Landau sampling. Use of a numerically efficient, density-functional theory validated interatomic potential [1] allows for extensive sampling in simulation cells large enough to appropriately capture the long-range disorder. The determined configurational ensemble is indeed characterized by a large degree of microscopic inhomogeneity. Subsequent room-temperature molecular dynamics simulations reveal the dominant fraction of Li ions in this ensemble to be immobile on nanosecond timescales. However, certain disorder motifs give rise to a novel correlated ion diffusion mechanism. We discuss this mechanism in the context of the evolution and morphology of the so-called two-phase reaction appearing during Li intercalation [2].

[1] M. Vijayakumar et al., J. Power Sources 196, 2211 (2011)

[2] M. G. Verde et al., ACS Nano 10, 4312 (2016)

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