Lithium bis(fluorosulfonyl)imide-based liquid electrolytes are promising for realizing high coulombic efficiency and long cycle life in next-generation Li-metal batteries. However, the role of anions in the formation of the solid–electrolyte interphase remains unclear. Here we combine electrochemical analyses and X-ray photoelectron spectroscopy measurements, both with and without sample washing, together with computational simulations, to propose the reaction pathways of electrolyte decomposition and correlate the interphase component solubility with the efficacy of passivation. We discover that not all the products derived from interphase-forming reactions are incorporated into the resulting passivation layer, with a notable portion present in the liquid electrolyte. We also find that the high-performance electrolytes can afford a sufficiently passivating interphase with minimized electrolyte decomposition, by incorporating more anion-decomposition products. Overall, this work presents a systematic approach of coupling electrochemical and surface analyses to paint a comprehensive picture of solid–electrolyte interphase formation, while identifying the key attributes of high-performance electrolytes to guide future designs.

基于双（氟磺酰基）酰亚胺锂的液体电解质有望在下一代锂金属电池中实现高库仑效率和长循环寿命。然而，阴离子在固体-电解质界面形成中的作用仍不清楚。在这里，我们将电化学分析和 X 射线光电子能谱测量（有和没有样品清洗）与计算模拟相结合，提出了电解质分解的反应途径，并将相间组分溶解度与钝化的功效相关联。我们发现，并非所有来自相间形成反应的产物都掺入所得的钝化层中，其中很大一部分存在于液体电解质中。我们还发现，通过掺入更多的阴离子分解产物，高性能电解质可以提供足够的钝化界面，并最大限度地减少电解质分解。总体而言，这项工作提出了一种耦合电化学和表面分析的系统方法，以描绘固体电解质界面形成的全面图景，同时确定高性能电解质的关键属性以指导未来的设计。