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Local electronic structure variation resulting in Li ‘filament’ formation within solid electrolytes


Solid electrolytes hold great promise for enabling the use of Li metal anodes. The main problem is that during cycling, Li can infiltrate along grain boundaries and cause short circuits, resulting in potentially catastrophic battery failure. At present, this phenomenon is not well understood. Here, through electron microscopy measurements on a representative system, Li7La3Zr2O12, we discover that Li infiltration in solid oxide electrolytes is strongly associated with local electronic band structure. About half of the Li7La3Zr2O12 grain boundaries were found to have a reduced bandgap, around 1–3 eV, making them potential channels for leakage current. Instead of combining with electrons at the cathode, Li+ ions are hence prematurely reduced by electrons at grain boundaries, forming local Li filaments. The eventual interconnection of these filaments results in a short circuit. Our discovery reveals that the grain-boundary electronic conductivity must be a primary concern for optimization in future solid-state battery design.

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Fig. 1: Atomic and electronic structure difference at the grain bulk and GBs of pristine LLZO.
Fig. 2: The d.c. cycling test of LLZO and microscopy images of LLZO after dendrite penetration.
Fig. 3: In situ TEM observation of the LLZO GB during biasing.
Fig. 4: The structure and chemistry evolution at the grain bulk and GB during biasing.
Fig. 5: Schematic illustrations.

Data availability

The data that support the findings of this study are available from the corresponding authors upon reasonable request.


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This work was initiated as part of a project supported by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. Technique developments and M.C.’s efforts on analysis and manuscript preparation were supported by DOE Basic Energy Sciences early career award no. ERKCZ55. Microscopy was conducted at Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. A.S. and J.S. acknowledge support from the DOE Advanced Battery Material Research programme grant no. DE-EE00006821. Y.C. acknowledges computing resources made available through the VirtuES project, funded by Laboratory Directed Research and Development programme and Compute and Data Environment for Science (CADES). C.M. acknowledges support from the National Key R&D Program of China (2018YFA0209600, 2017YFA0208300), the National Natural Science Foundation of China (51802302) and the Fundamental Research Funds for the Central Universities (WK2060190085, WK3430000006). M.C. thanks R. Erni at ETH Zurich for the valuable discussions on valence-EELS analysis. Part of the research was conducted using instrumentation within ORNL’s Materials Characterization Core provided by UT-Batelle under contract no. DE-AC05-00OR22725 with the DOE.

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Authors and Affiliations



M.C. conceived the study. X.L. performed the TEM, EELS, SEM and EDX. R.G.-M., A.S. and J.S. performed the LLZO synthesis, electrochemical measurements and electron backscatter diffraction. A.R.L., J.C.I. and M.C. performed the valence-EELS experiments and carried out the related analysis. C.W. and F.H. performed SEM characterizations. Y.C. performed density functional theory calculations. M.C., C.W., C.M., Y.C. and J.S. interpreted the results. C.M. and X.L. wrote the manuscript. All authors contributed to the discussion of the results and the manuscript editing.

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Correspondence to Cheng Ma, Jeff Sakamoto or Miaofang Chi.

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The authors declare no competing interests.

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Liu, X., Garcia-Mendez, R., Lupini, A.R. et al. Local electronic structure variation resulting in Li ‘filament’ formation within solid electrolytes. Nat. Mater. 20, 1485–1490 (2021).

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