Guidelines for Correlative Imaging and Analysis of Reactive Lithium Metal Battery Materials

To unlock the full potential of lithium metal batteries, a deep understanding of lithium metal’s reactivity and its solid electrolyte interphase (SEI) is essential. Correlative imaging, combining focused ion beam (FIB) and electron microscopy (EM), offers a powerful approach for multi-scale characterization. However, the extreme reactivity of lithium metal and its SEI presents challenges in investigating deposition and stripping mechanisms. In this work, we systematically evaluated the storage stability of lithium metal in a glove box (Ar atmosphere, <0.1 ppm moisture and oxygen) before and after electrochemical deposition. We then assessed different FIB ion sources (Ga⁺, Xe⁺, Ar⁺) for their impact on lithium metal lamella preparation for transmission electron microscopy (TEM). Furthermore, we examined cryogenic-TEM (cryo-EM) transfer methods, optimizing for minimal contamination during sample handling. Contrary to prior assumptions, we demonstrate that atomic-resolution imaging of pure lithium metal at room temperature is achievable using inert gas sample transfer (IGST) with an electron dose rate exceeding 10^3 e/Å^2 * s, without significant damage. In contrast, SEI components, such as Li2CO3, and LiF, display much greater sensitivity to electron beams, requiring cryogenic conditions and precise dose control for atomic-scale imaging. We quantified electron dose limits for these SEI compounds to track their structural evolution under irradiation. Based on these findings, we propose a robust protocol for lithium metal sample handling—from storage to atomic-level characterization—minimizing damage and contamination. This work paves the way for more accurate and reproducible studies, accelerating the development of next-generation lithium metal batteries by ensuring the preservation of native material properties during analysis.