Obtaining a better understanding of activation volumes in ionic conductors
Final Report Abstract
In literature, microscopic activation volumes correspond to the volume change in the atomic structure of a material during an ion jump and can be determined thermodynamically from pressure dependent conductivity measurements. Na+ and Li+ conductors were investigated in this project. Although there is no clear trend for Na3PnS4 (Pn = P, Sb), the activation volumes were found to increase with increasing Br−/S2− site disorder. Motivated to further examine if the concept of the migration volume (Vm) can be applied to argyrodites, the crystallographic volume and migration volume were investigated. In collaboration with the group of Prof. Karsten Albe, the crystallographic volume was calculated by ab-initio molecular dynamics, and the migration volume was found to increase in Li+ argyrodites, even though the mobile ion (Li+) is the same, suggesting that the Li+ volume at the transition site is not constant. Since the structural changes that solid electrolytes undergo under pressure have yet to be explored experimentally, the project continued to investigate how external pressure induces structural changes in solid electrolytes. The 10% Br/S Li6PS5Br was initially investigated under applying uniaxial and hydrostatic pressure of 1.5 GPa. The strain induced was monitored using both lab X-ray powder diffraction (ex situ) and synchrotron high-pressure X-ray powder diffraction (in situ). In collaboration with the group of Prof. Hubert Huppertz, the material was pressed at 10 GPa, where no amorphization or phase transition was observed but higher induced permanent strain. The strain was attributed to the formation of dislocations and a two-fold increase in the room-temperature ionic conductivity of the strained material was found. The effect of pressure on the structure of Na3PnS4 was then also investigated. In situ synchrotron high-pressure powder X-ray diffraction shows a tetragonal-to-cubic phase transition at pressures of 2.9 GPa for Na3SbS4 and 14.6 GPa for Na3PS4. Rietveld refinements and symmetry analysis provided insights into the displacive phase transition mechanism, related to the motion of Na+ and the rotation of the SbS43− tetrahedra. Density functional theory calculations confirmed that the cubic phase becomes thermodynamically favorable under high pressure compared to the tetragonal phase.
Publications
-
Oral Presentation at MRS Fall Meeting & Exhibit, Boston, USA, December 2022. Faka, V.; Agne, M. T.; Zeier, W.G. “Investigation of activation volumes of site disordered Li6PS5Br”
Faka, V.; Agne, M. T. & Zeier, W.G.
-
Poster Presentation at International Bunsen Discussion Meeting Solid-state Batteries V (SSB V), Frankfurt, Germany, November 2022. Faka, V.; Agne, M. T.; Zeier, W.G. ‘’Pressure dependence of site disordered Li6PS5Br’’
Faka, V.; Agne, M. T. & Zeier, W.G.
-
Pressure dependence of ionic conductivity in site disordered lithium superionic argyrodite Li6PS5Br. Energy Advances, 2(11), 1915-1925.
Faka, Vasiliki; Agne, Matthias T.; Till, Paul; Bernges, Tim; Sadowski, Marcel; Gautam, Ajay; Albe, Karsten & Zeier, Wolfgang G.
-
Oral Presentation at Solid State Chemistry Seminar (GRS), New London, United States, July 20 - 21, 2024. Faka, V. “Exploring the Influence of Pressure on Structural and Transport Properties in Solid Electrolytes”
Faka, V.
-
Oral Presentation at Solid State Ionics 2024 – 3E3 Battery Materials, London, U.K., 15th – 19th July, 2024. Faka, V. “How does pressure affect the structure and transport properties of Li+ argyrodites?”
Faka, V.
-
Poster Presentation at Solid State Chemistry (GRC), New London, United States, July 21 - 26, 2024 Faka, V.; Agne, M. T.; Lange M.A. Zeier, W.G. “The influence of pressure in Li+ argyrodites”
Faka, V. & Agne, M. T.
-
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.
-
Solid Ion Conductors under Pressure: In Situ Monitoring of the Tetragonal to Cubic Phase Transition of Na3SbS4 and Na3PS4. ACS Materials Letters, 7(7), 2648-2654.
Faka, Vasiliki; Lange, Martin A.; Daisenberger, Dominik; Böger, Thorben; Martinez de Irujo-Labalde, Xabier; Fallon, M. Jewels; Kieslich, Gregor & Zeier, Wolfgang G.
