Carlos Wexler - University of Missouri

Wednesday 5 Mar 2025, 08:00 → 19:15 US/Eastern

IAMM

Prof. Wexler’s group uses a combination of theoretical modeling and computer simulations to investigate “nano-sponges”—materials with pores in the nanometer scale—that are capable of storing hydrogen and natural gas (methane) reversibly by physisorption at moderate pressures. In particular Wexler seeks to understand how the nanopores can be engineered (optimal pore size and geometry, chemical surface functionaliation) to enhance the hydrogen-pore interaction.

https://physics.missouri.edu/people/wexler

08:30 → 09:00 Pick up at hotel

Travel to IAMM.

Speaker: Prof. Adrian Del Maestro (University of Tennessee, Knoxville)

09:00 → 10:00 Adrian Del Maestro - Research Meeting

Speaker: Prof. Adrian Del Maestro (University of Tennessee, Knoxville)

10:00 → 10:20 Talk Prep

10:20 → 11:20 Improving Li Diffusion in Solid State Electrolytes by Neutron Irradiation Induced Vacancies: Combined Theoretical and Experimental Study

Solid state electrolytes (SSE) have the potential to enhance the performance of batteries, fuel cells and supercapacitors due to the fact that they are non-flammable, would not have the potential to leak toxic organic compounds, can perform better at higher temperatures and would suppress the growth of metal dendrites. However, most SSE’s have small ionic conductivities vs. that of their liquid counterparts. A variety of SSE’s are of interest; in this talk we focus in LiBO2 in a path to explore other (more promising) materials. LiBO2 ionic conductivity is very low (~10^-6–10^-5 S/cm), requiring improvement. Here we consider the effect of lattice vacancies in the Li-ion transport. In particular, B vacancies can be produced relatively uniformly through the sample by means of thermal neutron irradiation, e.g., through the boron neutron capture reaction ¹⁰B + ¹n → ⁷Li + ⁴He + 2.79 MeV. By means of density functional theory (DFT) calculations we show that B vacancies significantly reduce the activation energy (Em) of Li-ion transport in both monoclinic (α phase) and tetragonal (γ phase) polymorphs of LBO2 leading to a significant enhancement of the ionic conductivity (in contrast, while O vacancies lower Em in m-LBO2, they increase it in t-LBO2) [1]. Experimentally, monoclinic (α phase) polycrystalline LiBO2 powders were pressed into pellets and irradiated with thermal neutrons at the University of Missouri Research Reactor (MURR). X-ray diffraction (XRD) shows no new crystalline phases, suggesting that neutron irradiation does not significantly degrade the crystal structure. Scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) show systematic dose-dependent changes of surface microstructure and chemistry, indicating the presence of neutron-induced defects, such as B vacancies. Electrochemical impedance spectroscopy (EIS) shows a ~30% increase of the ionic conductivity of pellets irradiated 60 minutes, suggesting that thermal neutron irradiation might be a viable strategy to improve the ionic conductivity of LiBO2.

[1] C. Ziemke, HM Nguyen, S. Amaya-Roncancio, J. Ghal, Y. Xing, T.W. Heitmann, and C. Wexler, Formation of lattice vacancies and their effects on lithium-ion transport in LiBO2 crystals: comparative ab initio studies, J. Mater. Chem. A 13, 3146 (2025).

Funded in part by MU Materials Science and Engineering Institute Grant CD002339 and MURR. We acknowledge the computing infrastructure provided by MU Research Support Services.

Speaker: Carlos Wexler (University of Missouri)

11:30 → 12:00 Research Meeting

Speaker: Claudia Rawn (University of Tennessee)

12:00 → 13:30 Lunch

13:30 → 14:00 Research Meeting

Speaker: Yang Zhang

14:00 → 14:30 Research Meeting

Speaker: Amber White (University of Tennessee)

14:30 → 15:00 Research Meeting

Speaker: Wonhee Ko (University of Tennessee, Knoxville)

15:00 → 15:30 Research Meeting

Speaker: Jonathan D'Emidio

15:30 → 16:00 Research Meeting

Speaker: Hanno Weitering

16:00 → 16:30 Research Meeting

16:30 → 17:00 Research Meeting

17:00 → 17:30 Research Meeting

Speaker: Hatem Barghathi

17:45 → 19:15 Dinner

Adrian Del Maestro