碳酸氟乙烯酯对硅锂离子电极上固体电解质界面的影响,Chemistry of Materials

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碳酸氟乙烯酯对硅锂离子电极上固体电解质界面的影响
Chemistry of Materials ( IF 7.2 ) Pub Date : 2015-08-11 00:00:00 , DOI: 10.1021/acs.chemmater.5b01627
Kjell Schroder ₁ , Judith Alvarado ₂ , Thomas A. Yersak ₂ , Juchuan Li ₃ , Nancy Dudney ₃ , Lauren J. Webb ₁ , Ying Shirley Meng ₂ , Keith J. Stevenson ₁

Affiliation

碳酸氟亚乙酯（FEC）已成为与硅负极一起使用的标准电解质添加剂，但是FEC如何影响硅阳极表面上的固体电解质相（SEI）的形成仍不为人所知。在此，由LiPF ₆组成的SEI在50 nm厚的非晶硅薄膜电极上研究了含FEC和不含FEC的碳酸盐电解质，以了解FEC在硅电极表面反应中的作用。与以前的工作相反，无水和缺氧技术被用来防止空气和湿气污染已制备的SEI膜。这允许通过X射线光电子能谱和飞行时间二次离子质谱深度分析对SEI结构和成分进行准确表征。这些结果表明，FEC还原会导致氟离子和LiF的形成，这与以前的计算和实验结果一致。令人惊讶地，我们还发现这些物质降低了锂离子的溶解度并增加了硅表面的反应性。

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The Effect of Fluoroethylene Carbonate as an Additive on the Solid Electrolyte Interphase on Silicon Lithium-Ion Electrodes

Fluoroethylene carbonate (FEC) has become a standard electrolyte additive for use with silicon negative electrodes, but how FEC affects solid electrolyte interphase (SEI) formation on the silicon anode’s surface is still not well understood. Herein, SEI formed from LiPF₆-based carbonate electrolytes, with and without FEC, were investigated on 50 nm thick amorphous silicon thin film electrodes to understand the role of FEC on silicon electrode surface reactions. In contrast to previous work, anhydrous and anoxic techniques were used to prevent air and moisture contamination of prepared SEI films. This allowed for accurate characterization of the SEI structure and composition by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry depth profiling. These results show that FEC reduction leads to fluoride ion and LiF formation, consistent with previous computational and experimental results. Surprisingly, we also find that these species decrease lithium-ion solubility and increase the reactivity of the silicon surface. We conclude that the effectiveness of FEC at improving the Coulombic efficiency and capacity retention is due to fluoride ion formation from reduction of the electrolyte, which leads to the chemical attack of any silicon-oxide surface passivation layers and the formation of a kinetically stable SEI comprising predominately lithium fluoride and lithium oxide.

更新日期：2015-08-11

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