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 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 connections to the measured ionic, thermal and electronic transport properties.

Influence of lattice dynamics on ionic transport

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Soft, polarizable anion lattices have always been thought to influence ionic mobility in solids. Our group aims to understand this influence of the dynamics of the lattice on the ionic conductivity in solid electrolytes.

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
  • Krauskopf et al. "Influence of lattice dynamics on Na-transport in the solid electrolyte Na3PS4-xSex“ Chem. Mater. 2017 doi:10.1021/acs.chemmater.7b03474
  • Krauskopf T. et al. "Comparing the descriptors for investigating the influence of lattice dynamics on ionic transport using the superionic conductor Na3PS4-xSex” J. Am. Chem. Soc. 2018 doi:10.1021/jacs.8b09340

Structural chemistry of ionic conductors

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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+) within a material’s structure and employ synthetic strategies to increase the diffusion pathways and ionic conductivity. The materials we study are oxides, phosphates, sulfides and thio-phosphate lithium ion conductors.

Selected Publications

  • Weber D.A. et al. “Structural insights and 3D diffusion pathways within the lithium superionic conductor Li10GeP2S12” Chem. Mater. 2016, 28 (16), 5905-5915 doi:10.1021/acs.chemmater.6b02424
  • Minafra N. et al. “Effect of Si substitution on the structural and transport properties of superionic Li-argyrodites” J. Mater. Chem. A 2018, 6, 645-651 doi:10.1039/C7TA08581H
  • Krauskopf T. et al. “The bottleneck of diffusion and inductive effects in Li10Ge1-xSnxP2S12” Chem Mater. 2018, 30, 1791-1798 doi:10.1021/acs.chemmater.8b00266
  • Dietrich C. et al. "Lithium ion conductivity in Li2S-P2S5 glasses - Building units and local structure evolution during crystallization of the superionic conductors Li3PS4, Li7P3S11 and Li4P2S7" J. Mater. Chem. A 2017, 5, 18111-18199 doi:10.1039/C7TA06067J

Interfacial chemistry of all-solid-state batteries

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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. In order to assess the performance and future of all-solid-state batteries we investigate the occurring interfacial processes using in situspectroscopic techniques and time-resolved electrochemistry.

Selected Publications

  • Janek J., Zeier W.G., “A solid future for battery development” Nat. Energy 2016, 1 (9), 16141 doi:10.1021/10.1038/nenergy.2016.141
  • Koerver R. et al. "Redox-active cathode interphases in solid-state batteries“ J. Mater. Chem. A 2017, 5, 22750-22760 doi:10.1039/C7TA07641J
  • Koerver R. et al. “Capacity fade in solid-state batteries: Interphase formation and chemo-mechanical processes in nickel-rich layered oxide cathodes and lithium thiophosphate solid electrolytes” Chem. Mater. 2017, 29, 5574-5582 doi:10.1021/acs.chemmater.7b00931
  • Zhang W. et al. “(Electro)chemical expansion during cycling: monitoring pressure changes in operating solid-state lithium batteries” J. Mater. Chem.

Influencing thermoelectric transport using crystal chemistry

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Thermoelectric materials convert thermal energy into electrical energy. The efficiency of a thermoelectric material strongly depends on properties such as the thermopower, electrical and thermal conductivity. We probe how the transport behavior of these materials changes when the composition and the structures are strategically altered. We are currently working on a deeper understanding of how local bonding interactions influence the electric and thermal transport behavior.

Selected Publications

  • Zeier W.G. et al. “Engineering half-Heusler thermoelectric materials using Zintl chemistry“ Nature Rev. Mater. 2016, 16032 – doi:10.1038/natrevmats.2016.32
  • Zeier W.G. et al. “Thinking like a chemist: intuition in thermoelectric materials“ Angew. Chem. Int. Ed. 2016, 55 (24), 6826-6841, doi:10.1002/anie.201508381
  • Hanus R. et al. “A chemical understanding for the band convergence in CoSb3 skutterudites: influence of electron population, local thermal expansion and bonding interactions” Chem. Mater. 2017, 29, 1156-1164 doi:10.1021/acs.chemmater.6b04506