by Shuang Bai, Zhao Liu, Diyi Cheng, Bingyu Lu, Nestor J. Zaluzec, Ganesh Raghavendran, Shen Wang, Thomas S. Marchese, Brandon van Leer, Letian Li, Lin Jiang, Adam Stokes, Joseph P. Cline, Rachel Osmundsen, Minda Chen, Paul Barends, Alexander Bright, Minghao Zhang & Ying Shirley Meng
Understanding how reactive alkali metals behave during battery operation is central to advancing next-generation energy storage, yet their extreme sensitivity to air, moisture, and electron or ion probes has long limited reliable characterization. Lithium and sodium metals, along with their solid electrolyte interphases (SEIs), undergo rapid chemical and beam-induced transformations that can obscure their native structure. This study establishes a unified framework—from storage and focused ion beam (FIB) preparation to transfer and electron microscopy—that clarifies when cryogenic conditions are essential and when room-temperature imaging is feasible. A key conceptual finding is that metallic alkali phases and their SEIs possess fundamentally different beam tolerances: lithium metal can be imaged at atomic resolution at room temperature if air exposure is eliminated, whereas common SEI components such as Li2CO3 and LiF require low-dose cryogenic conditions to avoid artificial reduction or decomposition.
Equally important, this work reveals that widely used preparation tools can introduce substantial artifacts unless chemical reactivity is explicitly considered. Inert plasma FIB sources such as Xe+ or Ar+ mill alkali metals without structural distortion, while conventional Ga+ FIB induces alloying and morphological damage. By quantifying dose limits, defining reliable transfer protocols, and identifying sources of artifacts, this framework enables reproducible, artifact-free imaging across length scales. It provides the broader energy community with a standardized foundation for probing reactive metal interfaces critical to high-performance alkali metal batteries.