Lithium (Li) penetration through solid electrolytes (SEs) induces short circuits in Li solid-state batteries (SSBs), which is a critical issue that hinders the development of high energy density SSBs. While cracking in ceramic SEs has been often shown to accompany Li penetration, the interplay between Li deposition and cracking remains elusive. Here, we constructed a mesoscale SSB inside a focused ion beam-scanning electron microscope (FIB-SEM) for in situ observation of Li deposition-induced cracking in SEs at nanometer resolution. Our results revealed that Li propagated predominantly along transgranular cracks in a garnet Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO). Cracks appeared to initiate from the interior of LLZTO beneath the electrode surface and then propagated by curving toward the LLZTO surface. The resulting bowl-shaped cracks resemble those from hydraulic fracture caused by high fluid pressure on the surface of internal cracks, suggesting that the Li deposition-induced pressure is the major driving force of crack initiation and propagation. The high pressure generated by Li deposition is further supported by in situ observation of the flow of filled Li between the crack flanks, causing crack widening and propagation. This work unveils the dynamic interplay between Li deposition and cracking in SEs and provides insight into the mitigation of Li dendrite penetration in SSBs.

Using a generalized quasi-continuum method, we characterize the post-buckling morphologies and energetics of thick multi-walled carbon nanotubes (MWCNTs) under uniaxial compression. Our simulations identify for the first time evolving post-buckling morphologies, ranging from asymmetric periodic rippling to a helical diamond pattern. We attribute the evolving morphologies to the coordinated buckling of the constituent shells. The post-buckling morphologies result in significantly reduced effective moduli that are strongly dependent on the aspect ratio. Our simulation results provide fundamental principles to guide the future design of high-performance, MWCNT-based nanodevices.