2024 IRG-1: Elucidating Electrostatics at Grain Boundaries in Perovskite Solid Electrolytes Using 4D-STEM
The main achievement of this research is revealing the atomic-scale origin of the low grain-boundary (GB) resistance in air-quenched (Li0.375Sr0.4375)(Ta0.375Nb0.375Zr0.125Hf0.125)O3 (LSTNZH) perovskite solid electrolyte in charge perspective and providing insights on overcoming the ubiquitous bottleneck of high GB resistance by elemental selection and material processing.
Significance of this scientific achievement
· Applying four-dimensional scanning transmission electron microscopy (4D-STEM) on solid-state electrolytes for the first time, we present an in-depth study of the atomic structure and electrostatic properties of GBs in quenched LSTNZH, furnace-cooled LSTNZH and base material Li0.375Sr0.4375Ta0.75Zr0.25O3 (LSTZ).
· Aberration-corrected STEM and energy dispersive X-ray spectroscopy (EDS) were used to reveal the atomic scale structures and compositions of GBs in these three samples, suggesting elemental segregation exists at the GBs of air-quenched LSTNZH while absents at the GBs of the other two.
· Density functional theory (DFT) calculation was applied, revealing the preference that Ta tends to distribute in grain bulk while Nb tends to accumulate at GBs. Furthermore, charge density difference was calculated before and after the elemental redistribution and calculations agree with experiments well.
· Based on these results, the authors 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.
Contribution to IRG 1
This study provides new insights into the nano-scale mechanisms of low GB resistance and sheds light on possible paths for designing compositionally complex oxide solid electrolytes with high total ionic conductivity.
C. Du, T. Lee, Y. Huang, T. Aoki, Z.K. Wang, X. Pan (University of California, Irvine)
Z.S. Wang, S. Ko, J. Qi, J. Luo, S. P. Ong (University of California, San Diego)