title: Interfacial Stability of Li Metal-Solid Electrolyte Elucidated via in Situ Electron Microscopy.
abstract: Despite their different chemistries, novel energy-storage systems, e.g., Li-air, Li-S, all-solid-state Li batteries, etc., face one critical challenge of forming a conductive and stable interface between Li metal and a solid electrolyte. An accurate understanding of the formation mechanism and the exact structure and chemistry of the rarely existing benign interfaces, such as the Li-cubic-Li7-3xAlxLa3Zr2O12(c-LLZO) interface, is crucial for enabling the use of Li metal anodes. Due to spatial confinement and structural and chemical complications, current investigations are largely limited to theoretical calculations. Here, through an in situ formation of Li-c-LLZO interfaces inside an aberration-corrected scanning transmission electron microscope, we successfully reveal the interfacial chemical and structural progression. Upon contact with Li metal, the LLZO surface is reduced, which is accompanied by the simultaneous implantation of Li+, resulting in a tetragonal-like LLZO interphase that stabilizes at an extremely small thickness of around five unit cells. This interphase effectively prevented further interfacial reactions without compromising the ionic conductivity. Although the cubic-to-tetragonal transition is typically undesired during LLZO synthesis, the similar structural change was found to be the likely key to the observed benign interface. These insights provide a new perspective for designing Li-solid electrolyte interfaces that can enable the use of Li metal anodes in next-generation batteries.
authors.forename: Cheng
authors.initials: C
authors.lastname: Ma
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Cheng
authors.forename: Kuibo
authors.initials: K
authors.lastname: Yin
authors.affiliation: Department of NanoEngineering, University of California at San Diego , La Jolla, California 92093, United States.
authors.forename: Jian
authors.initials: J
authors.lastname: Luo
authors.affiliation: Department of Mechanical Engineering, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Asma
authors.initials: A
authors.lastname: Sharafi
authors.affiliation: Department of Mechanical Engineering, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Jeff
authors.initials: J
authors.lastname: Sakamoto
authors.forename: Juchuan
authors.initials: J
authors.lastname: Li
authors.forename: Karren L
authors.initials: KL
authors.lastname: More
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Dudney
authors.forename: Miaofang
authors.initials: M
authors.lastname: Chi
keywords: Solid electrolytes; electron microscopy; in situ; interface; lithium metal; passivation; stability