Berlin 2015 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 23: Methods in Computational Materials Modelling: Battery Mateirals
MM 23.1: Vortrag
Dienstag, 17. März 2015, 11:45–12:00, H 0106
Electronic structure of oxygen-deficient Li4Ti5O12−δ — Saskia Stegmaier, •Christoph Scheurer, and Karsten Reuter — Technische Universität München, Germany
The lithium titanate Li4Ti5O12 (LTO) is a promising alternative anode material for rechargeable lithium-ion batteries which offers advantageous materials properties in terms of safety and stability. The low electronic conductivity of pristine Li4Ti5O12, however, is a drawback. LTO samples with an increased electronic conductivity have been prepared, for example, via routes including thermal treatment in reducing atmosphere. Under these conditions, oxygen vacancies are formed and Ti4+ ions are reduced. Experimental XPS and EPR data indicate the presence of discrete Ti3+ and Ti4+ ions rather than a full delocalization of the extra electrons.[1,2]
Such oxygen-deficient materials with mixed-valent metal cations pose a challenge to computational materials modeling with density-functional theory (DFT) methods since calculations with standard LDA or GGA functionals only lead to a delocalized picture of the charge distribution. DFT+U calculations can be employed to capture spatial localization of excess electrons on transition metal sites but the choice of the Hubbard U parameter introduces some ambiguity. We thus performed DFT calculations with hybrid functionals in order to gain a more reliable first principles based insight into the defect chemistry and electronic structure of oxygen-deficient Li4Ti5O12−δ.
[1] J. Wolfenstine, J. L. Allen, J. Power Sources 2008, 180, 582.
[2] H. Song et al., Sci. Rep. 2014, 4, 4350.