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

Xiaoming Liu; Regina Garcia-Mendez; Andrew R Lupini; Yongqiang Cheng; Zachary D Hood; Fudong Han; Asma Sharafi; Juan Carlos Idrobo; Nancy J Dudney; Chunsheng Wang; Cheng Ma; Jeff Sakamoto; Miaofang Chi

doi:10.1038/s41563-021-01019-x

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

Nat Mater. 2021 Nov;20(11):1485-1490. doi: 10.1038/s41563-021-01019-x. Epub 2021 May 31.

Authors

Affiliations

¹ Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
² Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA.
³ Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
⁴ School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, USA.
⁵ Department of Chemical and Bimolecular Engineering, University of Maryland, College Park, MD, USA.
⁶ Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
⁷ Hefei National Laboratory for Physical Sciences at the Microscale, Department of Materials Science and Engineering, CAS Key Laboratory of Materials for Energy Conversion, University of Science and Technology of China, Hefei, China. mach16@ustc.edu.cn.
⁸ Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI, USA. jeffsaka@umich.edu.
⁹ Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA. chim@ornl.gov.

^# Contributed equally.

PMID: 34059815
DOI: 10.1038/s41563-021-01019-x

Abstract

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.