物理化学学报 >> 2020, Vol. 36 >> Issue (11): 1910067.doi: 10.3866/PKU.WHXB201910067

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[C3mim][NTf2]/DEC/[Li][NTf2]体系的基础性质

惠淑荣1, 赵丽薇1, 刘青山2,*(), 宋大勇2,*()   

  1. 1 沈阳农业大学理学院,沈阳 110866
    2 湖州师范学院生命科学学院,浙江 湖州 313000
  • 收稿日期:2019-10-03 录用日期:2019-11-25 发布日期:2019-11-29
  • 通讯作者: 刘青山,宋大勇 E-mail:02726@zjhu.edu.cn;chsdyq@163.com
  • 基金资助:
    国家留学基金委(201608210093)

Basic Properties of [C3mim][NTf2]/DEC/[Li][NTf2] Systems

Shurong Hui1, Liwei Zhao1, Qingshan Liu2,*(), Dayong Song2,*()   

  1. 1 College of Science, Shenyang Agricultural University, Shenyang 110866, P. R. China
    2 School of Life Sciences, Huzhou University, Huzhou 313000, Zhejiang Province, P. R. China
  • Received:2019-10-03 Accepted:2019-11-25 Published:2019-11-29
  • Contact: Qingshan Liu,Dayong Song E-mail:02726@zjhu.edu.cn;chsdyq@163.com
  • Supported by:
    the China Scholarship Council with Reference(201608210093)

摘要:

本文通过传统方法合成了1-丙基-3-甲基咪唑双三氟甲基磺酸亚胺疏水型离子液体,在离子液体中加入碳酸二乙酯和双三氟甲基磺酸亚胺锂盐制备了八个体系。通过差式扫描量热仪考察了上述体系的热力学性质。考察了体系的半稳定态温度随着锂盐的加入后的变化情况,以及玻璃化温度随离子液体与碳酸二乙酯的比例的变化情况。测量结果并没有观测到体系的熔点温度,表明碳酸二乙酯和锂盐能够在较低的温度下溶解在离子液体中。系统研究了不同温度下八个体系的基础性质,如:锂离子([Li]+)自扩散系数随碳酸二乙酯浓度的变化规律,密度、粘度和电导率随温度的变化规律,利用Vogel Fulcher Tamman (VFT),Final Vogel Fulcher Tamman (FVFT)和Arrhenius方程计算得到八个体系的粘度活化能、电导活化能等。在性质实验的基础上,通过分子动力学模拟讨论了[Li]+与[NTf2]-/碳酸二乙酯之间的相互作用情况,及碳酸二乙酯的引入对LiNTf2/离子液体体系的微观结构影响,其中阴离子[NTf2]-通过氧原子与锂离子之间发生相互作用。通过径向分布函数和对[Li]+周围O原子的配位数的分析表明,碳酸二乙酯的引入,削弱了[Li]+与[NTf2]-之间的相互作用。因此,碳酸二乙酯的引入有利于[Li]+的扩散,该结论与实验结果相符。

关键词: 离子液体, 碳酸二乙酯, 双三氟甲基磺酸亚胺锂, 基础性质

Abstract:

The hydrophobic ionic liquid (IL) 1-propyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C3mim][NTf2]) was synthesized according to traditional methods. By adding different amounts of diethyl carbonate (DEC) solvent and lithium bis[(trifluoromethyl)sulfonyl]imide ([Li][NTf2]) salt to [C3mim][NTf2] IL, eight solution systems were prepared. First, the thermodynamic properties of the eight solution systems were characterized by differential scanning calorimetry (DSC). The semi-stable temperature of the system gradually disappeared with increasing lithium salt content, but the melting point temperature was not apparent in the experiment. These results indicate that DEC and lithium salts can dissolve in ILs within the tested temperature range. The basic properties of the eight systems, including thermodynamic and dynamic properties, were systematically studied at different temperatures. The variation in the self-diffusion coefficient of lithium ion ([Li]+) as a function of DEC concentration, density changes, viscosity, conductivity, and the viscosity/conductivity activation energy of the eight systems was calculated by the Vogel Fulcher Taman (VFT), Final Vogel Fulcher Taman (FVFT), and Arrhenius equations. The effect of temperature on the properties of the system was studied in detail. Within the temperature range measured herein, the deviation between the fitting equation and experimental value was small. Consequently, these equations were successfully used to calculate the properties of the system at various temperatures. All fitting parameters of the corresponding equations are provided herein. The viscosity for all systems decreased rapidly with increasing temperature, which increased the conductivity. Based on these experiments, the influence of DEC on the system microstructure was discussed in the context of the molecular dynamics simulation results. In particular, the interaction between [Li]+ and [NTf2]-/DEC was examined. In all solution systems, [NTf2]- coordinates to [Li]+ through only the O atom and not the N atom. Radial distribution function (RDF) analysis showed that the interaction between [Li]+ and [NTf2]- weakened with increasing DEC concentration. DEC molecules were observed in the first solvation layer of [Li]+ coordinating to [Li]+ through the carbonyl O atom. Although the interaction between [Li]+ and DEC was weakened, competition between [NTf2]- and DEC in the first solvation layer of [Li]+ was observed by the coordination number analysis of the O atom around [Li]+. Therefore, the introduction of DEC is beneficial for Li+ diffusion, which is consistent with the experimental results.

Key words: Ionic liquids, Diethyl carbonate, Lithium bis[(trifluoromethyl)sulfonyl]imide, Basic property

MSC2000: 

  • O642