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Atomic-scale origin of the low grain-boundary resistance in perovskite solid electrolyte Li0.375Sr0.4375Ta0.75Zr0.25O3

The main goal of this research is to reveal the atomic-scale origin of the low grain-boundary (GB) resistance in Li0.375Sr0.4375Ta0.75Zr0.25O3 (LSTZ0.75) perovskite solid electrolyte and to provide insights on overcoming the ubiquitous bottleneck of high GB resistance in other oxide solid electrolytes.

Scientific highlight
· Aberration-corrected scanning transmission electron microscopy and spectroscopy, along with an active learning moment tensor potential, were used to reveal the atomic scale structure and composition of LSTZ0.75 GBs.
· Li depletion, which is a major cause for the low GB ionic conductivity of Li3xLa2/3-xTiO3 (LLTO), was found to be absent for the GBs of LSTZ0.75.
· A unique defective cubic perovskite interfacial structure that contained abundant vacancies was discovered at the GBs of LSTZ0.75. We attributed the low GB resistance of LSTZ0.75 to this microstructure.
· Based on our results, we conclude vacancy and defect engineering can effectively improve GB ionic conductivity of solid Li-ion conductors, given that the material’s original structural framework should be maintained.

Scientific impact
This study provides new insights into the atomic-scale mechanisms of low GB resistance and sheds light on possible paths for designing oxide solid electrolytes with high total ionic conductivity.