Abstract text (incl. figure legends and references)

Lithium metal is one of the most promising anode candidate for the next-gen solid state battery. To go through the hurdles for a reliable and cost effective solid state battery, it is crucial to build strong fundamental understandings of different parts of a battery at microscopy level. Techniques such as site-specific DualBeam (FIB-SEM) lamella preparation and subsequent TEM analysis have always been the key steps to unlock atomic resolution for materials science studies. However, due to the air and moisture sensitivity associated with various battery components (Li metal, SEI layer, Solid electrolyte), it used to be a very challenging task to keep sample integrity during the workflow, especially during sample transfer between different instruments.

In the current study, an novel IGST (Inert Gas Sample Transfer) workflow solution was used to enable a DualBeam to TEM workflow by protecting both the bulk sample and the prepared lamella in Ar atmosphere with a inert gas transfer module (CleanConnect).

Using the CleanConnect module, a bulk Li-metal piece was successfully transferred from glovebox to a DualBeam without signs of surface oxidation. Due to the low melting point of lithium, the entire TEM lamella preparation process, including bulk milling, lift out, attach to TEM grid and final thinning were carried out at cryogenic temperature (-178C) with a LN2 cooled cryo-stage and cryo-nano-manipulator. To achieve minimal ion damage to the final lamella, all the ion milling processes were carried out with Ar plasma focused ion beam.

The prepared lamella was then transferred back to glovebox under Ar gas protection using CleanConnect transfer module. Inside the glovebox, the lamella was loaded to a IGST double tilt TEM holder, which allows lamella transfer from glovebox to a CFEG TEM under Ar gas protection.

The lamella was then analyzed in TEM. It is evident that the whole workflow successfully protects the lithium metal lamella from oxidation during transfer between multiple instruments. The lithium metal lamella stays crystalline with minimal signs of surface oxidation. Atomic resolution TEM images from lithium metal were successfully acquired. According to literature survey, this could be the first DualBeam prepared lithium lamella which gives atomic resolution in TEM analysis. EELs maps from the lamella were acquired to quantify the amount of oxidation on the Lithium lamella. It was found that the amount of Oxygen were below 1.8 at%, which validates the results. After the TEM analysis, the lamella were delibrately exposed in atomophere for less than 15 sec, significant oxidation were observed after the exposure, which further proves the necessity of the IGST workflow.

The study successfully shows the capability of the workflow by achieving atomic resolution from Li-metal, which is one of the most challenging samples in terms of air, moisture, and temperature sensitivity. The success of the workflow also enables new methods to study other trending topics in the battery world such as characterization of SEI layer evolution, post-mortem analysis in higher resolution whilst keeping the sample in its original state.