Journal
ADVANCED ENERGY MATERIALS
Volume 9, Issue 12, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/aenm.201803440
Keywords
buried interface; Li metal; solid electrolytes; solid-state batteries; surface science
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Funding
- U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Office
- Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division
- U.S. Department of Energy, Office of Science
- DOE Office of Science [DE-AC02-06CH11357]
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Li7La3Zr2O12(LLZO) garnet-based materials doped with Al, Nb, or Ta to stabilize the Li+-conductive cubic phase are a particularly promising class of solid electrolytes for all-solid-state lithium metal batteries. Understanding of the intrinsic reactivity between solid electrolytes and relevant electrode materials is crucial to developing high voltage solid-state batteries with long lifetimes. Using a novel, surface science-based approach to characterize the intrinsic reactivity of the Li-solid electrolyte interface, it is determined that, surprisingly, some degree of Zr reduction takes place for all three dopant types, with the extent of reduction increasing as Ta < Nb < Al. Significant reduction of Nb also takes place for Nb-doped LLZO, with electrochemical impedance spectroscopy (EIS) of Li parallel to Nb-LLZO parallel to Li symmetric cells further revealing significant increases in impedance with time and suggesting that the Nb reduction propagates into the bulk. Density functional theory (DFT) calculations reveal that Nb-doped material shows a strong preference for Nb dopants toward the interface between LLZO and Li, while Ta does not exhibit a similar preference. EIS and DFT results, coupled with the observed reduction of Zr at the interface, are consistent with the formation of an oxygen-deficient interphase (ODI) layer whose structure determines the stability of the LLZO-Li interface.
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