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Native Defects and their Doping Response in the Lithium Solid Electrolyte Li7La3Zr2O12

preprint
revised on 22.10.2019 and posted on 23.10.2019 by Alex Squires, David Scanlon, Benjamin Morgan

The Li-stuffed garnets LixM2M3′O12 are promising Li-ion solid electrolytes with potential use in solid-state batteries. One strategy for optimising ionic conductivities in these materials is to tune lithium stoichiometries through aliovalent doping, which is often assumed to produce proportionate numbers of charge compensating Li vacancies. The native defect chemistry of the Li-stuffed garnets, and their response to doping, however, are not well understood, and it is unknown to what degree a simple vacancy-compensation model is valid. Here, we report hybrid density-functional–theory calculations of a broad range of native defects in the prototypical Li-garnet Li7La3Zr2O12. We calculate equilibrium defect concentrations as a function of synthesis conditions, and model the response of these defect populations to extrinsic doping. We predict a rich defect chemistry that includes Li and O vacancies and interstitials, and significant numbers of cation-antisite defects. Under reducing conditions, O vacancies act as colour-centres by trapping electrons. We find that supervalent (donor) doping does not produce charge compensating Li vacancies under all synthesis conditions; under Li-rich / Zr-poor conditions the dominant compensating defects are LiZr antisites, and Li stoichiometries strongly deviate from those predicted by simple “vacancy compensation” models.

Funding

EP/N001982/1

EP/P00315X/1

UF130329

EP/S003053/1 FIRG003

EP/L000202

EP/R029431

History

Email Address of Submitting Author

b.j.morgan@bath.ac.uk

Institution

University of Bath

Country

United Kingdom

ORCID For Submitting Author

0000-0002-3056-8233

Declaration of Conflict of Interest

No conflict of interest

Version Notes

Version 1.1

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