Figure presents an overview of the experiment setup, a representative current-voltage curve, and operando SEM images of the lithium-plating process. In all experiments, we employ freshly fractured, phase-pure Ta-doped LLZO (transported from a dedicated LLZO glovebox to the SEM using an air-free transfer system) to ensure a chemically pristine interface, similar to previous work . We acknowledge that this preparation route may lead to different defects on the surface compared to other preparation methods such as polishing or tape casting. To initiate each experiment, the tungsten microprobe is brought into contact with the LLZO surface in a region without any obvious microstructural defects (large pores, cracks, etc.). The contact force is quantified via a spring table located inside the SEM. Upon performing linear sweep voltammetry, we observe rapid growth of lithium-metal whiskers on the surface of the LLZO (at about Vapp < |-0.1| V), as shown in Figure .