fig5

Figure 5. (A) X-ray tomographic reconstructions of voids within LLZO samples sintered at (a) 1,050, (b) 1,100, and (c) 1,150 °C. The changes in pore size distribution between the pristine and failed electrolytes are shown in (d-f) for 1,050, 1,100, and 1,150 °C. Reprinted (adapted) with permission from Shen et al.^[123]. Copyright (2018) American Chemical Society. (B) Illustration of trans-granular and inter-granular Li metal plating through polycrystalline LLZO and optical and SEM images of a cycled LLZO pellet showing the appearance of black linear features caused by the propagation of metallic Li. This figure is quoted with permission from Cheng et al.^[124]. (C) Photographs of garnet pellets before and after shorting. After shorting, the garnet surface facing the NMC cathode becomes yellow with numerous black lines and spots. The dark spots reveal potential Li dendrites on the cycled garnet pellet. In the backscattered electron (BSE) SEM image of the garnet surface facing the cathode after cycling, the dark area is likely the deposited Li. Scheme of the reversible short-circuit in the garnet-based full cell, in which the short-circuit happens in the charging stage but disappears in the discharging stage. This figure is quoted with permission from Ping et al.^[127]. (D) Optical image of Li penetration with different types or morphologies, and SEM images together with the schematic illustration of straight type, branching type, spalling type, and diffuse type Li-penetration. This figure is quoted with permission from Kazyak et al.^[130]. (E) (a and b) Optical micrographs of Cu current collectors and associated Li tree structures. (c) BSE SEM image of the area, shown in the first optical images and (d) cross-sectional BSE SEM image of the battery. (e) Zoomed-in BSE SEM image with associated Energy Dispersive Spectroscopy (EDX) analysis of the end of one of the tree structures. This figure is quoted with permission from Westover et al.^[131].