Li Coordination of a Novel Asymmetric Anion in Ionic Liquid-in-Li Salt Electrolytes
Li Coordination of a Novel Asymmetric Anion in Ionic Liquid-in-Li Salt Electrolytes
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DOI：
10.1021/acs.jpcb.9b11051
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发表时间：
2020-02-06
影响因子：
3.3
通讯作者：
Schoenhoff, Monika
中科院分区：
文献类型：
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作者：
Nuernberg, Pinchas;Lozinskaya, Elena, I;Schoenhoff, Monika
我们分析了锂盐/离子液体体系中阴离子的不对称性对配位和输运过程的影响。在Pyr（14）TFSAM（（1-x））LiTFSAMx中，在宽的浓度范围内（x = 0.7Li盐）研究了相对较新的不对称2，2，2-三氟甲磺酰基-N-氰胺（TFSAM）阴离子，并与已知的双（三氟甲磺酰基）酰胺（TFSA）阴离子进行了比较.与基于TFSA的系统相比，具有TFSAM的系统在整个浓度范围内没有相变。拉曼光谱和NMR化学位移详细阐明了Li配位。当x = 0.3时，不对称阴离子仅通过氰基与Li+配位。随着Li盐含量的增加，Li-氧配位的贡献增加。通过脉冲场梯度核磁共振（PFG-NMR）研究，这种配位效应影响系统的输运性质。虽然这两个系统的整体扩散率由于粘度效应而降低，但Li阳离子的相对扩散率随着x而增加。这表明取决于Li盐分数的传输机制的变化。有趣的是，在高锂盐浓度（x >= 0.6）的结构扩散的贡献似乎是较高的TFSAM系统中，受非对称的协调，而在TFSA系统中，车辆运输似乎仍然是占主导地位的x >= 0.6。
We analyze the influence of the asymmetry of the anion on coordination and transport processes in a Li salt/ionic liquid system. The relatively new asymmetric 2,2,2-trifluoromethylsulfonyl-N-cyanamide (TFSAM) anion was investigated in Pyr(14)TFSAM((1-x))LiTFSAMx over a broad concentration range (up to x = 0.7 Li salt) and was compared to the well-known bis(trifluoromethanesulfonyl)amide (TFSA) anion. In contrast to the TFSA-based system, the system with TFSAM has no phase transition over the whole concentration range. Raman spectroscopy and NMR chemical shifts elucidate the Li coordination in detail. Up to x = 0.3, the asymmetric anion coordinates to Li+ only via the cyano group. With increasing Li salt fraction, the contribution of Li-oxygen coordination increases. This coordination effects influence the transport properties of the system, as examined via pulsed-field-gradient NMR (PFG-NMR). Although the overall diffusivity of both systems is decreasing because of viscosity effects, the relative diffusivity of the Li cation is increasing with x. This suggests a change in the transport mechanism depending on the Li salt fraction. Interestingly, the contribution of structural diffusion at high Li salt concentrations (x >= 0.6) seems to be higher in the TFSAM system, influenced by the nonsymmetric coordination, while in the TFSA system, the vehicular transport seems to be still predominant at x >= 0.6.