Figure shows high-resolution SEM images of lithium intrusions in plan-view and cross section geometries after electrochemistry was performed. After lithium intrusions appear in the LLZO, narrow cracks are observed within the solid electrolyte, as shown in Figure . At most locations, the cracks are barely visible via SEM with crack widths < 30 nm. From the FIB cross section, we did not observe a significant change in porosity, or any lithium metal isolated from the crack network.