Investigation of grain boundary and local structure of Sr-doped LLZO with high Li-ion conductivity

Grain boundary and local structure of Sr-doped Li-excess garnet Li7+xLa3−xSrxZr2O12 (Sr-doped LLZO) with enhanced Li-ion conductivity were examined in this study. Cross-sectional observation by scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) revealed that the formation of the grain boundary structure is suppressed by the addition of Sr to LLZO. Local structural analysis on La and Zr sites by X-ray absorption near edge structure (XANES) revealed an actively changed structure around the Zr site, which was not observed around the La site where Sr is substituted. Furthermore, the XANES spectral changes suggest two types of Li conduction path structures in Sr-substituted LLZO.