Materials by Design

Our work seeks the understanding of the underlying structural chemistry of functional materials and its effects on their physical properties by using a combination of synthetic structural chemistry, solid-state physics, and solid-state electrochemistry. On the synthetic side, we employ classical solid-state syntheses (oxides, chalcogenides, and thiophosphates) as well as gas flow techniques, sol-gel synthesis, mechanochemical- and microwave-assisted synthesis, and flux growth of crystals. Multiple structural characterization techniques (X-ray scattering, neutron scattering and pair-distribution function analyses) help us understand the local structural arrangements and bonding interactions and provide correlations to the measured ionic, thermal, and electronic transport properties.

 

Solid-state batteries

All-solid-state batteries are the next-generation battery technology, with the hope to replace the current liquid electrolytes for increased safety and higher energy density, if lithium metal anodes and solid electrolytes are used. To assess the performance and future of all-solid-state batteries we investigate the occurring interfacial processes using in spectroscopic techniques and time-resolved electrochemistry. In addition, a major focus of the group is the identification of the partial transport properties in composites employing diverse active materials (NMC, Sulfur, Silicon), tuned solid electrolytes and conductive additives, which are linked to the preparation of the composites themselves.

Selected Publications

• Janek J., Zeier W.G, “Challenges in speeding up solid-state battery development” Nature Energy 2023, 8, 230-240 doi:10.1038/s41560-023-01208-9
• Schlautmann E., et al. „Impact of the solid electrolyte particle size distribution in sulfide-based solid-state battery composites” Adv. Energy Mater. 2023 doi:10.1002/aenm.202302309
• Rosenbach C., et al.  "Visualizing the Chemical Incompatibility of Halide and Sulfide-Based Electrolytes in Solid-State Batteries" Adv. Energy Mater. 2023, 13, 2203673 doi:10.1002/aenm.202203673

Structural chemistry of ionic conductors

Ionic conductors are used in many applications such as fuel cells and batteries, and a high ionic conductivity is usually desired. We aim to understand the motion of ions (e.g. Li+, Na+) within a material’s structure and employ synthetic strategies to increase the diffusion pathways and ionic conductivity. The materials we study are oxides (especially phosphates), sulfides especially thiophosphate as well as halide lithium- and sodium-ion conductors. By combining a variety of transport measurements and structural characterizations, guidelines for understanding and optimizing the transport in various materials are established.

 

Selected Publications

• Ohno S., et al., „Materials design of ionic conductors for solid state batteries“ Prog. Energy 2020 doi:10.1088/2516-1083/ab73dd
• Culver S.P., et al.  „Designing ionic conductors: the interplay between structural phenomena and interfaces in thiophosphate-based solid-state batteries” Chem. Mater. 2018, 30, 4179-4192 doi:10.1021/acs.chemmater.8b01293
• Schlem R., et al. „Energy storage materials for solid-state batteries: design by mechanochemistry” Adv. Energy Mater. 2021, 2101022 doi:10.1002/aenm.202101022

Local structures of materials

Using pair distribution function analyses we explore the local structure (short-range order) of functional materials. Developed predominantly for liquids and glasses, the total scattering experiment derived from wide-angle X-ray diffraction allows investigation of glass-ceramics and nanoparticles. We however mainly employ it for the exploration of the local structure complementary to the average structures (long range order), their differences, as well as their influence on the transport in ionic conductors.

 

Selected Publications

• Maus O., et al “On the discrepancy between local and average structure in the fast Na+ ionic conductor Na2.9Sb0.9W0.1S4” J. Am. Chem. Soc. 2023, 145, 7147-7158 doi:19.1021/jacs.2c11803
• Schlem R., et al.  „Mechanochemical synthesis, a tool to tune cation site-disorder and ionic transport properties of Li3MCl6 (M = Y, Er) superionic conductors” Adv. Energy Mater. 2020, 19033719 doi:10.1002/aenm.201903719

Thermal transport and lattice dynamics in ionic conductors

Soft, polarizable anion lattices have always been thought to beneficially influence ionic mobility in solids. Our group aims to understand this influence of the phonon properties (describing dynamics of the lattice) on the ionic conductivity in solid electrolytes. In addition, by learning how lattice dynamics play a role in ionic conductors, we explore the interrelation between thermal and ionic transport.

 

Selected Publications

• Kraft et al. "On the 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:10.1021/jacs.7b06327
• Muy S., et al. „Phonon – ion interactions: designing ion mobility based on lattice dynamics” Adv. Energy Mater. 2021, 2002787

• Agne M.T., et al. "Importance of Thermal Transport for the Design of Solid-State Battery Materials" PRX Energy 2022, 1, 031002 doi:10.1103/PRXEnergy.1.031002

• Bernges T., et al. „Considering the role of ion transport in diffuson-dominated thermal conductivity” Adv. Energy Mater. 2022, 2200717 doi:10.1021/aenm202200717