Dresden 2017 – wissenschaftliches Programm
MM 19: SYLI: Symposium Interfacial Challenges in Solid-State Li Ion Batteries - sulphate- and phosphate-based electrolytes
MM 19.2: Vortrag
Montag, 20. März 2017, 17:30–17:45, IFW A
Defect chemistry of solid electrolyte Li4P2S6 by first-principles calculations — •Marcel Sadowski, Sabrina Sicolo, and Karsten Albe — Institute of Materials Science, Technische Universität Darmstadt, Jovanka-Bontschits-Str. 2, 64287 Darmstadt, Germany
Glassy, glass-ceramic and crystalline lithium thiophosphates have attracted interest as solid electrolytes for all-solid-state batteries. Despite similar structural motifs, these materials exhibit a wide range of compositions, structures and ionic conductivities. For the glass-ceramic consisting of crystalline Li4P2S6 and glassy Li4P2S7, for example, contradictory ionic conductivities were reported. In this contribution we present density functional theory (DFT) calculations on the defect thermodynamics and kinetics of crystalline Li4P2S6.  Despite the existence of low energy diffusion paths, the overall conductivity is inhibited by high defect formation energies. This supports the hypothesis that the conductivity of the Li4P2S7/Li4P2S6 composite material is determined by the relative amount of glassy and crystalline phases.
Furthermore, thermodynamics predict the instability of Li4P2S6 against metallic lithium. Corresponding interface models for different surface terminations of Li4P2S6 show the barrierless formation of an interphase reminiscent of Li2S, which might act as a passivating layer and protect the electrolyte from further decomposition.
 C. Dietrich, M. Sadowski, S. Sicolo, D. A. Weber, S. J. Sedlmaier, K. S. Weldert, S. Indris, K. Albe, J. Janek, W. G. Zeier, Chem. Mater. DOI:*10.1021/acs.chemmater.6b04175 (2016).