Superionic Fluorinated Halide Solid Electrolytes for Highly Stable Li‐Metal in All‐Solid‐State Li Batteries

作者：Yu Tianwei; Liang Jianwen; Luo Liang; Wang Limin; Zhao Feipeng; Xu Guofeng; Bai Xiangtao; Yang Rong; Zhao Shangqian; Wang Jiantao; Yu Jinqiu; Sun Xueliang

来源：Advanced Energy Materials, 2021, 11(36): 2101915.

DOI：10.1002/AENM.202101915

• all‐solid‐state lithium batteries
• halides
• in situ interfaces
• lithium metal anodes

The halide solid‐state electrolytes (SSEs) have received significant attention due to their high ionic conductivity and desirable compatibility with cathode materials. However, the reduction potential of the halide is still >0.6 V (versus Li/Li+). Reduction stability is still one of the challenges that need to be addressed. The fluorides have a wide electrochemical stability window due to the large electronegativity of F–. In contrast, Li3YBr6 (LYB) bromides have a narrower electrochemical window, although they have high lithium ion conductivity (>10–3 S cm–1). Herein, a fluorine doping strategy is employed. The interfacial stability between fluoride‐doped bromides and lithium metal is researched by cycling of lithium symmetric cells. Li plating/stripping can maintain over 1000 h at 0.75 mA cm–2. Interfacial protection mechanisms investigated by X‐ray photoelectron spectroscopy. A fluoride‐rich interfacial layer is formed in si...