Key considerations for preparing ion-milled lithium metal cross-sectional samples

Abstract Detailed understanding of lithium anode morphology is essential for solid-state battery technology development. Non-optimal interfacial contacts and structural changes during cycling present significant challenges, limiting both battery performance and wide adoption of solid-state batteries. Cross-sectional sample preparation combined with advanced electron microscopy techniques provides essential insights into the internal microstructure and composition of materials, particularly at critical interfaces. Visualizing degradation is crucial for identifying failure mechanisms and optimizing material performance. This paper explores the temperature dependence of ion-polished cross-sections, offers detailed guidelines for lithium cross-section preparation using a Ga+ Focused Ion Beam Scanning Electron Microscope (FIB-SEM) system, and compares the results to cross-sections prepared with an Ar+ ion polisher. We demonstrate that artifacts introduced during lithium cross-sectioning at room temperature can be eliminated by conducting the preparation at cryogenic temperatures of −100 °C or lower, regardless of the type of ions used in the sputtering process. This guidance helps ensure researchers generate quality cross-sections when evaluating this important field.