Li+ local structure in Li-tetraglyme solvate ionic liquid revealed by neutron total scattering experiments with the 6/7Li isotopic substitution technique
Li+ local structure in Li-tetraglyme solvate ionic liquid revealed by neutron total scattering experiments with the 6/7Li isotopic substitution technique
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6/7Li同位素取代技术中子全散射实验揭示了锂-四甘醇二甲醚溶剂化物离子液体中的锂局域结构
DOI：
10.1021/acs.jpclett.6b01266
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
Yasuhiro Umebayashi
中科院分区：
文献类型：
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作者：
Soshi Saito;Hikari Watanabe;Yutaka Hayashi;Masaru Matsugami;Seiji Tsuzuki;Shiro Seki;Jose N Canongia Lopes;Rob Atkin;Kazuhide Ueno;Kaoru Dokko;Masayoshi Watanabe;Yasuo Kameda;Yasuhiro Umebayashi
双（三氟甲磺酰基）氨基锂（LiTFSA）和四甘醇二甲醚（G4：CH 3 O-（CH 2CH 2 O）4-CH 3）的等摩尔混合物产生溶剂化物（或螯合物）离子液体[Li（G4）][TFSA]，其在室温下是均匀透明的溶液。溶剂化离子液体（Solvate ionic liquids，锡尔斯）作为锂硫电池的新型电解质，近年来受到越来越多的关注。在此，我们进行了6/7 Li同位素替代的中子全散射实验，以揭示[Li（G4）][TFSA]锡尔斯中Li+的溶剂化/局域结构。Li+周围的实验干涉函数和径向分布函数与从头计算和分子动力学模拟的预测吻合得很好。模型的溶剂化/局部结构进行了优化与非线性最小二乘分析，以产生结构参数。[Li（G4）][TFSA] SIL中的精细Li+溶剂化/局部结构表明，锂阳离子并不与G4分子的所有五个氧原子配位（缺乏五配位），而仅与其中四个氧原子配位（实际四配位）。因此，溶剂合物阳离子是相当扭曲的，这可以归因于有限的相空间的环氧乙烷链和竞争从TFSA阴离子的配位位点。
Equimolar mixtures of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and tetraglyme (G4: CH3O–(CH2CH2O)4–CH3) yield the solvate (or chelate) ionic liquid [Li(G4)][TFSA], which is a homogeneous transparent solution at room temperature. Solvate ionic liquids (SILs) are currently attracting increasing research interest, especially as new electrolytes for Li–sulfur batteries. Here, we performed neutron total scattering experiments with6/7Li isotopic substitution to reveal the Li+solvation/local structure in [Li(G4)][TFSA] SILs. The experimental interference function and radial distribution function around Li+agree well with predictions from ab initio calculations and MD simulations. The model solvation/local structure was optimized with nonlinear least-squares analysis to yield structural parameters. The refined Li+solvation/local structure in the [Li(G4)][TFSA] SIL shows that lithium cations are not coordinated to all five oxygen atoms of the G4 molecule (deficient five-coordination) but only to four of them (actual four-coordination). The solvate cation is thus considerably distorted, which can be ascribed to the limited phase space of the ethylene oxide chain and competition for coordination sites from the TFSA anion.