Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 50: Oxide and Insulator Surfaces I
O 50.7: Vortrag
Mittwoch, 2. April 2014, 12:00–12:15, WIL A317
The role of surfaces and interfaces in the phase separating Li intercalation material LixFeSiO4 — •Nicolas G. Hörmann1,2 and Axel Groß1,2 — 1Helmholtz Institute Ulm (HIU) Electrochemical Energy Storage, Albert-Einstein-Allee 11, 89069 Ulm — 2Universität Ulm, Institut für Theoretische Chemie, Albert-Einstein-Allee 11, 89069 Ulm
Phase separating behavior of electrode materials of secondary Li battery materials is typically assumed to cause low rate capability due to a nucleation and growth process. Nevertheless, cathodes made of LiFePO4 can show fast charging rates if they consist of nanoscale particles. Several mechanisms have been proposed for this observation, most of which are related to finite size effects such as interfaces or strain [1]. It is, however, still under debate whether e.g. the alignment of phase interfaces is mainly driven by "lattice" or "chemical mismatch" and how the actual interface looks like.
We present ab-initio studies tackling related issues for the promising material LixFeSiO4 [2] based on density functional theory (DFT). In particular, Li binding energies for different chemical environments - in bulk and near surfaces or interfaces - are determined. Effects of strain are considered by decomposing the interface energy into contributions due to coherency strain and change of the chemical environment. Subtleties such as charge localisation are analysed as well.
[1] Malik, R et al., J. Electrochem. Soc., 160, 5, A3179-A3197, 2013
[2] Hörmann, N.G. and Groß, A. , J. Solid State Electrochem., accept.