Abstract
Cubic Li7−3xAlxLa3Zr2O12 (LLZO) is a promising, next-generation solid electrolyte due to its stability with Li-metal and high bulk conductivity (∼1 mS cm−1). However, the source of the high conductivity is not completely understood. In this work, we address this key knowledge gap through the integration of elemental analysis, neutron diffraction sensitive to Li and O atoms, and impedance spectroscopy to understand the structure-property correlations for LLZO. We show the metal-oxygen framework structure remains constant with variation in Al substitution, resulting in a constant activation energy of ∼0.35 eV and little effect on the bulk conductivity. Instead, Li concentration, Al blocking and trapping of mobile defects, and Li-Li nearest neighbor interactions largely control the Al substituted LLZO bulk conductivity, resulting in decreases from 0.73 to 0.22 mS cm−1 as the Al concentration increases from 0.17 to 0.32 mol. These results differ from those of Ta substituted LLZO, where the framework structure and Li-Li site distances play large roles in controlling the conductivity. The increased understanding of the controlling factors of conductivity allows for greater ability to tailor the design of and substitution into the LLZO structure for improved conductivity.
| Original language | English |
|---|---|
| Pages (from-to) | 28193-28210 |
| Number of pages | 18 |
| Journal | Journal of Materials Chemistry A |
| Volume | 12 |
| Issue number | 41 |
| DOIs | |
| State | Published - Sep 25 2024 |
Funding
A. C. M. would like to thank Jeffrey Einkauf and Diana Stamberga in ORNL's Chemical Separations Group for repeated access to the ICP used in this work and Amanda Musgrove for assistance in performing the ICP measurements. A. C. M would also like to thank Nicola Ashcroft and Brian Toby for helpful discussions. M. L. is grateful to Takeshi Egami for helpful discussions. This work was part of the US-German joint collaboration on “Interfaces and Interphases in Rechargeable Li-Metal Based Batteries” supported by the US Department of Energy (DOE) and the German Federal Ministry of Education and Research (BMBF) under DOE grant number DE-ACO5-000R22275 is acknowledged. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program. The SCGSR program is administered by the Oak Ridge Institute for Science and Education for the DOE under contract number DE-SC0014664. A. C. M. would like to thank the Rackham Graduate School at the University of Michigan for support through the Rackham Pre-Doctoral Fellowship. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by Oak Ridge National Laboratory (IPTS-27340.1 for POWGEN experiment) for supporting this research through its user program. A portion of this work (ICP, data analysis) was performed at the Oak Ridge National Laboratory (G. M. V.) and supported by U.S. Department of Energy's Vehicle Technologies Office under the US-Germany Consortium Project, directed by Tien Duong. This manuscript has been authored in part by UT-Battelle, LLC, under contract DEAC05-00OR22725 with the U.S. Department of Energy (DOE). The publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doepublic-accessplan).