CMSP Seminar (Atomistic Simulation Webinar Series): Understanding ion mobility mechanism using descriptors and scaling relations in solid crystals
Starts 8 Jun 2022 11:00
Ends 8 Jun 2022 12:00
Central European Time
In the area of sustainable energy storage and conversion, super ionic conductors have been attracting considerable attention due to their potential utility for electrochemical devices such as electrodes and solid electrolytes. Through density functional theory investigations, we have derived a descriptor for the ion mobility just based on easily accessible observables: ionic radii and oxidation states of the migrating cations and the anions of the host lattice, and the difference in their Pauling electronegativity. A statistical compressed-sensing approach using the sure-independence screening and sparsifying operator SISSO has been applied to verify our proposed descriptor. We find that the migration barriers are connected through linear scaling relations upon variation of either the cation chemistry of the charge carrier or the anion chemistry of the host lattice. This demonstrates the strong predictive power of the descriptor, which should accelerate the discovery of materials with improved migration properties in electrochemical energy storage and conversion .
We address the ionic conductivity in spinel host materials which represent a promising class of cathode and solid-electrolyte materials in battery technology. Based on the descriptor, we demonstrate that ionic mobility can be increased through the incorporation of rather electronegative cations from the 4d and 5d series. For instance, the conductivity of Mg2+ in Mg(Ir/Rh)2O4 materials compares well with those of Li+ in fast Li-ion conductors, such as Garnets. We will highlight the critical role trigonal distortions play in the ion mobility and show that it is the competition between coordination and bond length that governs the Mg site preference in ternary spinel compounds. This can only be understood by considering covalent interactions revealing that purely ionic interactions are not sufficient to understand mobility in crystalline battery materials. Furthermore, our calculations suggest a more important role of anionic redox in sulfide and selenide spinels than in oxide spinels.  We show that a fundamental understanding of the chemical interactions within transition metal chalcogenides is instrumental in offering guidelines aimed to increase the ion mobility in post Li-ion technologies resulting in a descriptor that allows to predict migration barrier energy.
Literature:  M. Sotoudeh and A. Groß JACS Au 2022, 2, 463–471  M. Sotoudeh, M. Dillenz, A. Groß, Adv. Energy Sustainability Res. 2021, 2, 2100113.