Ion conductors under pressure
Computer-Aided Design of Materials and Simulation of Materials Behaviour from Atomic to Microscopic Scale
Synthesis and Properties of Functional Materials
Physical Chemistry of Solids and Surfaces, Material Characterisation
Final Report Abstract
Currently common lithium-ion batteries operate using a liquid electrolyte. However, in order to enable more compact and lighter designs while reducing the risk of fire, solid-state batteries are increasingly becoming the focus of research. The current long-term tests of solid-state batteries by reputable companies in the automotive sector are promising, reaching up to 1,000 charge cycles, equivalent to a total range of 500,000 km. Both, during cell production and during charging and discharging, the materials used are subject to volume changes and therefore pressure fluctuations. This project investigated what happens to ion-conducting materials under pressure and which new ion-conducting materials can emerge under ambient and highpressure. Among other things, a 1000-ton multianvil press was used. For example, lithium molybdenum sulfide, LiMoS2, shows increased crystallinity under pressure, allowing the structure to be elucidated for the first time based on single-crystal data. Additionally, the layer spacing can be adjusted by varying the alkali metal, increasing linearly from LiMoS2 to NaMoS2 to KMoS2. For the known ion conductor Li6PS5Br (a Li+-conducting argyrodite), a doubling of ion conductivity was observed with increasing pressure up to 10 gigapascals (=100,000 bar), correlated with an increasing disruption of the regularity of the crystal structure (increasing dislocation densities). While the activation energy remains unchanged, the mechanism of ion conduction seems to change as the dislocation cores likely enable a new path for ion mobility. Furthermore, in this project, new compounds such as a high-temperature phase (HT) and a high-pressure phase (HP) of Cu1.8Sb5.4Se9, as well as a high-pressure phase of LiMoS2, were crystallized and characterized. Methods of computer-assisted theoretical chemistry were applied for structure prediction and interpretation. Calculating binding energies based on crystal structures with a modified bond valence sum approach (BVS) proved particularly helpful in calculating activation energies for ion conduction and visualizing pathways of ion conduction in the crystal structure. This was successfully demonstrated for the compounds HT- Cu1.8Sb5.4Se9, LiMoS2, and Li7Si2NO6. Additionally, the electronic properties of HT- Cu1.8Sb5.4Se9 were calculated using density functional theory.
Publications
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An Unexpected New Member of the Family of Lithium Oxonitridosilicates – Li7Si2NO6. European Journal of Inorganic Chemistry, 26(25).
Rießbeck, Kilian M.; Seibald, Markus; Schwarzmüller, Stefan; Baumann, Dominik & Huppertz, Hubert
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High-pressure/high-temperature synthesis of the first walstromite-analogue borate Tm2CrB3O9. Zeitschrift für Kristallographie - Crystalline Materials, 239(1-2), 27-33.
Teichtmeister, Tobias A.; Schwarzmüller, Stefan; Wurst, Klaus; Heymann, Gunter & Huppertz, Hubert
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High‐pressure/high‐temperature synthesis of Nd3B5O11(OH)2. Zeitschrift für anorganische und allgemeine Chemie, 650(1).
Teichtmeister, Tobias A.; Bernhart, Alexander Hugo; Schwarzmüller, Stefan; Wurst, Klaus & Huppertz, Hubert
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Pressure‐Assisted Synthesis of Highly Crystalline 1T′′‐LixMoS2. Chemistry – A European Journal, 30(5).
Schwarzmüller, Stefan; Wurst, Klaus; Heymann, Gunter & Huppertz, Hubert
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Pressure-Induced Dislocations and Their Influence on Ionic Transport in Li+-Conducting Argyrodites. Journal of the American Chemical Society, 146(2), 1710-1721.
Faka, Vasiliki; Agne, Matthias T.; Lange, Martin A.; Daisenberger, Dominik; Wankmiller, Björn; Schwarzmüller, Stefan; Huppertz, Hubert; Maus, Oliver; Helm, Bianca; Böger, Thorben; Hartel, Johannes; Gerdes, Josef Maximilian; Molaison, Jamie J.; Kieslich, Gregor; Hansen, Michael Ryan & Zeier, Wolfgang G.
