Relative solid electrolyte interphase (SEI) film thickness investigation on graphite electrodes after the first charge state in the lithium‐ion battery was successfully demonstrated by the ex‐situ small‐angle neutron scattering technique. Here, for both the mesophase graphite powder (MGP) and the fine‐mesophase graphite powder (FMGP) anodes, with two different particle sizes was analyzed precisely by the Guinier–Porod model. The data revealed a stable, maximum (~tens of nm) bi‐layer SEI film formed on MGP anode in ethylene‐carbonate/dimethyl‐carbonate (EC/DMC) at a capacity of 50 mAh/g and sluggish above 100 mAhg^‐1. The SEI formed on FMGP with and without 3 wt% fluoroethylene‐carbonate additive in EC/DMC showed the relative thickness greater than that only in ethylene‐carbonate/diethyl‐carbonate. Lithiation initiated the rapid SEI formation on the graphite surface and achieved a maximum thickness in the cell potential ≤0.2 V, and became thinner when the graphite particle expanded after Li⁺ intercalation. It was observed that the SEI thickness influenced the electrolytes and additives, which might ultimately impact battery performance. Our preliminary results make evident that small‐angle neutron scattering could be employed to better understand the complex microstructure solid electrolyte interphase formation and its accurate thickness, on a mesophase graphite anode.

中文翻译：

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小角度中子散射研究不同电解质在中间相石墨电极上形成固体电解质相间层

通过异位小角度中子散射技术成功地证明了锂离子电池首次充电后石墨电极的相对固体电解质相间（SEI）膜厚的研究。在这里，对于中间相石墨粉（MGP）和细中间相石墨粉（FMGP）阳极，均使用Guinier-Porod模型精确地分析了两种不同的粒径。数据显示，在碳酸亚乙酯/碳酸二甲酯（EC / DMC）中的MGP阳极上形成了稳定的，最大（约数十纳米）的双层SEI膜，容量为50 mAh / g，超过100 mAhg ^-1则反应缓慢。。在FMGP上在EC / DMC中添加和不添加3 wt％氟代碳酸亚乙酯时形成的SEI的相对厚度大于仅在碳酸亚乙酯/碳酸二乙酯中的相对厚度。锂化引发了在石墨表面上快速SEI的形成，并在单元电势≤0.2V时达到了最大厚度，并且当Li ⁺嵌入后石墨颗粒膨胀时，锂离子化变得更薄。据观察，SEI厚度会影响电解质和添加剂，最终可能会影响电池性能。我们的初步结果表明，小角度中子散射可用于更好地理解中间相石墨阳极上复杂的微结构固体电解质相间形成及其精确厚度。