Analysis of MD Simulations of Lithium diffusion in Amorphous Lithium Thiophosphate
By: Anastasia Ovchinnikov
Department: Chemistry & Biochemistry
Faculty Advisor: Dr. Nicole Adelstein
Studying anion diffusion mechanisms in solid electrolytes has the potential to help create safer and more efficient electrolytes that would improve battery safety and performance. Amorphous lithium thiophosphate is more conductive than its crystalline counterpart, so we are comparing their diffusion mechanisms to determine factors that can lead to faster conductivity in amorphous electrolytes. MD simulations of amorphous lithium thiophosphate were created at 4 different densities ranging from the crystalline density to the amorphous density using machine learning force fields. The lithium diffusion was simulated using first-principles molecular dynamics at 300K, 500K and 700K. We tracked Li jumps to study correlations between lithium cation diffusion and structural aspects in the solid. In our analysis density had no correlation with diffusion rate so we examined other structural factors such as PS4 anion rotations and defects such as PS3 or PS5 polyanions. If rotations or defects are known to affect diffusivity, they can be controlled in the synthesis process. Thus, our simulations can lead to more conductive solid electrolytes that would incorporated into next-generation all-solid-state batteries.