Abstract: Lithium-ion batteries are limited by the low energy density of graphite anodes and are gradually becoming unable to meet the demand for energy storage development. A further increase in high capacity requires new battery materials and chemistry, such as the innovative lithium metal anodes (LMAs). However, the actual commercialization of LMAs is limited by the unstable Li/electrolyte interface, impeding their progress from the laboratory to industrial production. To address these problems, constructing a Li alloy/Li halide mixed layer upon a Li surface is considered to be an ideal direction because of the combined advantages of Li alloys and Li halides. In this context, by comparing the limitations of self-generated solid electrolyte interfaces, the unique merits of Li alloys and Li halides are discussed in depth with summaries of their respective advances. Accordingly, mixed layers of Li alloy/Li halides are introduced, and the mechanisms of Li deposition behaviors are clearly described, along with their manufacturing strategies and recent progress. Moreover, the emerging techniques for interface characterization are also comprehensively summarized. Furthermore, the necessary considerations and outlooks for the future design of Li alloy/Li halide mixed layers are highlighted, with the aim of elucidating the structure-property relationships and providing rational directions for the attainment of the next-generation high-performance batteries.

Key words: Li alloy/halide mixed layers, Li/electrolyte interface, Electro-chemo-mechanical stability, Lithium metal batteries