Isotropic Raman scattering and time-of-flight neutron diffraction measurements were carried out for concentrated LiTFSA-EC solutions to obtain structural insight on solvated Li⁺ as well as the structure of contact ion pair, Li⁺···TFSA^–, formed in highly concentrated EC solutions. Symmetrical stretching vibrational mode of solvated Li⁺ and solvated Li⁺···TFSA^– ion pair were observed at ν = 168–177 and 202–224 cm^–1, respectively. Detailed structural properties of solvated Li⁺ and Li⁺···TFSA^– contact ion pair were derived from the least-squares fitting analysis of first-order difference function, Δ_Li(Q), between neutron scattering cross sections observed for ⁶Li/⁷Li isotopically substituted 10 and 25 mol % *LiTFSA-ECd₄ solutions. It has been revealed that Li⁺ in the 10 mol % LiTFSA solution is fully solvated by ca. 4 EC molecules. The nearest neighbor Li⁺···O(EC) distance and Li⁺···O(EC)═C(EC) bond angle are determined to be 1.90 ± 0.01 Å and 141 ± 1°, respectively. In highly concentrated 25 mol % LiTFSA-EC solution, the average solvation number of Li⁺ decreases to ca. 3 and ca. 1.5. TFSA^– are directly contacted to Li⁺. These results agree well with the results of band decomposition analyses of isotropic Raman spectra for intramolecular vibrational modes of both EC and TFSA^–.

中文翻译：

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低频拉曼散射和中子衍射与⁶ Li / ⁷ Li同位素取代方法研究浓缩碳酸亚乙酯溶液中Li ^+的局部结构

各向同性拉曼散射和时间飞行中子衍射测定对于浓缩LiTFSA的-EC溶液中进行，以获得对溶剂化的锂的结构洞察⁺以及接触离子对的结构中，锂⁺ ···TFSA ^- ，形成在高度浓缩的EC解决方案。Li ⁺和Li ⁺ ·· TFSA ^–离子对的对称拉伸振动模式分别在ν= 168–177和202–224 cm ^–1处观察到。Li ⁺和Li ⁺ ···TFSA溶剂化的详细结构特性^–接触离子对从最小二乘拟合的一阶差函数，Δ的分析导出_市里（Q），中子散射截面的观察之间⁶的Li / ⁷锂同位素取代的10和25％（摩尔）* LiTFSA的-EC d ₄解决方案。已经发现，在10mol％的LiTFSA溶液中的Li ⁺被约10％的溶剂完全溶解。4个EC分子。最近邻Li ⁺ ···O（EC）距离和Li ⁺ ··O（EC）═C（EC）的结合角分别确定为1.90±0.01Å和141±1°。在高浓度25 mol％LiTFSA-EC溶液中，Li ⁺的平均溶剂化数减少到大约 3和ca。1.5。TFSA ^–直接与Li ^+联系。这些结果与EC和TFSA ^–的分子内振动模式的各向同性拉曼光谱的能带分解分析结果非常吻合。