Januar
Bild des Monats Januar 2018
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Investigating the lattice dynamics in ionic conductors
Chemical intuition has always led to the believe that a softer, more polarizable anion sub-lattice of cation conductors leads to lower activation barriers for diffusion and subsequently higher ionic conductivities. This intuitive approach has been supported by the high conductivity of cations in iodine compounds compared to sulfides and oxides. However, until today, the chemical concept of increasing polarizability and softness of the lattice has never been experimentally proven within one materials class.
The group investigates this influence of a soft, dynamic lattice on the ionic transport in order to tailor the ionic conductivities of solid ion conductors for solid state batteries. We show that the paradigm “the softer, the better” is not entirely correct. While indeed a softer lattice changes the ion dynamics across activation barrier (see figure) the entropy of migration is also decreased. Our work shows that it is necessary to reinvestigate the theoretical descriptors for ionic conduction in the solid state.
Publications:
[1] Kraft M.A. et al. “Influence of lattice polarizability on the ionic conductivity in the lithium superionic argyrodites Li6PS5X (X = Cl, Br, I)” J. Am. Chem. Soc. 2017, 139, 10909-10918. doi: https://doi.org/10.1021/jacs.7b06327
[2] Krauskopf T. et al. “Influence of lattice dynamics on Na+ transport in the solid electrolyte Na3PS4-xSex” Chem. Mater. 2017, 29, 8859-8869. doi: https://doi.org/10.1021/acs.chemmater.7b03474
Dieses Bild wurde eingereicht von Dr. Wolfgang Zeier.