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MM: Fachverband Metall- und Materialphysik

MM 60: Topical Session: In Situ and Multimodal Microscopy in Materials Physics III

MM 60.3: Talk

Thursday, March 21, 2024, 16:15–16:30, C 130

Unusual field evaporation of lithium explained by first principles — •Shyam Katnagallu, Huan Zhao, Se-Ho Kim, Jörg Neugebauer, Baptiste Gault, and Christoph Freysoldt — Max-Planck-Institut für Eisenforschung, Max-Planck-Straße 1, 40237 Düsseldorf, Germany.

Lithium (Li) is a critical metal for battery operation due to its high energy density, low weight, and high mobility. To develop efficient batteries, atomic-scale characterization of complex, Li-containing materials is crucial. Atom probe tomography (APT) could provide extremely valuable insights. However, APT faces many evaporation artefacts that can render the data unusable, particularly for pure Li. We used density functional theory calculations that explicitly include high electric fields to investigate Li's field evaporation behavior from the close-packed Li(110) surface as a prototypical case. At low fields, Li preferentially adsorbs at on-top sites. We systematically study surface-diffusion of Li adatoms as a function of electric field, and discovered the existence of a "critical" electric field below the field strength at which Li evaporates, where the on-top site becomes energetically unfavourable compared to a hollow/bridge site. This leads to a practically barrier-less diffusion of Li atoms on the surface, which explains the spotty evaporation pattern observed experimentally. To prevent this undesired effect, we explored potential approaches to minimize surface diffusion before field evaporation. One approach involves depositing a monolayer of gas such as H, N, or He, onto the Li surface. We show that such an adsorbed gas layer prevents Li atoms from diffusing on the surface.

Keywords: Field evaporation; density functional theory; Lithium; atom probe