context: To directly observe and verify the possible contact loss between the cathode and solid electrolyte, FIB-SEM tomography was used to characterize the microstructural evolution in the composite cathode during cycling. Three SSB cells (before cycling, after 10 cycles, and after 50 cycles) were extracted in the discharged state and evaluated using FIB-SEM tomography. The workflow for the FIB-SEM tomography experiment is presented in Fig. 2. The SSB full cell was tilted at a 52° angle with the cathode composite perpendicular to the ion beam. The ion beam was first used to mill trenches surrounding the area of interest, exposing the cross-section to the top-mounted electron beam at a 52° angle. A backscattered electron (BSE) image was acquired to provide 2D morphology information on the cathode composite. Then, a thin slice (50 nm) was milled away from the cross-section with the ion beam, and another BSE image was taken. After repeating this process several hundred times, the image stack was aligned, cropped, and combined into a 2D image stack (Fig. 2(c)) (see ESI Fig. S2 and S3† for the detailed image process procedures). The 2D image stack and corresponding four-phase segmentation image are presented in Fig. 2(c) and (d), respectively, whereby the NMC cathode (blue), LPS solid electrolyte (yellow), carbon (black), and void (red) can be accurately distinguished. The segmented image stacks were then reconstructed into a 3D volume. The reconstructed structures of the composite cathodes before and after electrochemical cycling are presented in Fig. 3.
answer: NMC 