EIS and XPS Investigation on SEI Layer Formation during First Discharge on Graphite Electrode with a Vinylene Carbonate Doped Imidazolium Based Ionic Liquid Electrolyte,The Journal of Physical Chemistry C

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EIS and XPS Investigation on SEI Layer Formation during First Discharge on Graphite Electrode with a Vinylene Carbonate Doped Imidazolium Based Ionic Liquid Electrolyte
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2018-08-06 , DOI: 10.1021/acs.jpcc.8b03636
J. E. Morales-Ugarte _{1,

2} , E. Bolimowska _{2,

3} , H. Rouault _{1,

2} , J. Santos-Peña _{4,

5} , C. C. Santini ₃ , A. Benayad _{1,

2}

Affiliation

Adding organic carbonates (e.g., vinylene carbonates, VC) into ionic liquid based electrolyte generally improves the electrochemical performances of graphite electrode (Cgr) in lithium ion batteries. In this study, step-by-step electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) were performed during the first reduction cycle to follow the formation of the solid electrolyte interphase (SEI) in lithium/graphite (Li/Cgr) cell using (1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) [C₁C₆Im][NTf₂] doped with vinylene carbonate (VC). The EIS spectra evolution, recorded at different cutoff voltages, indicated a two-step SEI thin film formation. These results were supported by XPS measurement at the same cutoff voltage. Hence, we pointed out that the first film results from the VC decomposition at 0.8 V to form an organic layer constituted of lithium alkylcarbonates. This film was developed up to 0.2 V. From 0.8 to 0.2 V, we detected a slight decomposition of IL solvent. This process was driven by a progressive sulfone decomposition reaction through the formation of polyoxysulfone, Li₂S, Li₃N, and LiF. This process was at the origin of the formation of the second film of inorganic nature beyond 0.2 V. This SEI film was stable up to 0.01 V; the composition probed by XPS remained unchanged.

中文翻译：

碳酸亚乙烯酯掺杂的咪唑鎓离子液体电解质在石墨电极首次放电过程中SEI层形成的EIS和XPS研究

将有机碳酸酯（例如碳酸亚乙烯酯，VC）添加到基于离子液体的电解质中通常改善了锂离子电池中的石墨电极（Cgr）的电化学性能。在这项研究中，在第一个还原循环中进行了逐步电化学阻抗谱（EIS）和X射线光电子能谱（XPS），以追踪锂/石墨（Li /使用（1-己基-3-甲基咪唑双（三氟甲基磺酰基）酰亚胺）[C ₁ C ₆ Im] [NTf ₂掺杂有碳酸亚乙烯酯（VC）。在不同的截止电压下记录的EIS光谱演变表明，形成了两步SEI薄膜。在相同的截止电压下，通过XPS测量支持了这些结果。因此，我们指出第一膜是由0.8V下的VC分解形成的，形成了由烷基碳酸锂构成的有机层。将该膜显影至高达0.2V。从0.8到0.2 V，我们检测到IL溶剂略有分解。该过程是由逐步进行的砜分解反应推动的，该反应通过形成聚氧砜，Li ₂ S，Li _{3来进行。}N和LiF。此过程是在形成超过0.2 V的无机性质的第二层薄膜时开始的。此SEI薄膜在高达0.01 V的电压下是稳定的。XPS探测的成分保持不变。

更新日期：2018-08-07

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