Solvation structure around the Li+ ion in succinonitrile-lithium salt plastic crystalline electrolytes
Solvation structure around the Li+ ion in succinonitrile-lithium salt plastic crystalline electrolytes
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丁二腈-锂盐塑性结晶电解质中锂离子周围的溶剂化结构
DOI：
10.1039/c6cp02878k
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发表时间：
2016
影响因子：
3.3
通讯作者：
Yuan Kaijun
中科院分区：
文献类型：
--
作者：
Shen Yuneng;Deng Gang-Hua;Ge Chuanqi;Tian Yuhuan;Wu Guorong;Yang Xueming;Zheng Junrong;Yuan Kaijun
本文讨论了用超快振动光谱研究锂-丁二腈（SN）塑性结晶电解质的溶剂化动力学。红外吸收光谱表明，在同一溶液中，Li+结合和未结合的丁二腈分子的CN伸缩具有不同的振动频率（2276 cm−1vs. 2253 cm-1）。频率差使我们能够测量与Li+离子结合和未结合的溶剂分子的旋转衰减时间。发现Li+-SN络合物的Li+配位数在塑性晶体相（22 °C）中为2，在液相（80 °C）中为2.5-3，这与浓度无关（从0.05 mol kg−1到2 mol kg−1）。沿着讨论了Li ~+-SN配合物的溶剂化结构。此外，还测定了锂盐的离解百分率。在80 °C下，0.5 mol kg−1 LiBF 4-SN溶液中，60% ± 10%的盐解离成Li+，并与2或3个溶剂分子结合。在80 °C的0.5 mol kg−1 LiClO 4-SN溶液中，盐的解离率可高达90% ± 10%。
Herein, we discuss the study of solvation dynamics of lithium–succinonitrile (SN) plastic crystalline electrolytes by ultrafast vibrational spectroscopy. The infrared absorption spectra indicated that the CN stretch of the Li+ bound and unbound succinonitrile molecules in a same solution have distinct vibrational frequencies (2276 cm−1vs. 2253 cm−1). The frequency difference allowed us to measure the rotation decay times of solvent molecules bound and unbound to Li+ ion. The Li+ coordination number of the Li+–SN complex was found to be 2 in the plastic crystal phase (22 °C) and 2.5–3 in the liquid phase (80 °C), which is independent of the concentration (from 0.05 mol kg−1 to 2 mol kg−1). The solvation structures along with DFT calculations of the Li+–SN complex have been discussed. In addition, the dissociation percentage of lithium salt was also determined. In 0.5 mol kg−1 LiBF4–SN solutions at 80 °C, 60% ± 10% of the salt dissociates into Li+, which is bound by 2 or 3 solvent molecules. In the 0.5 mol kg−1 LiClO4–SN solutions at 80 °C, the salt dissociation ratio can be up to 90% ± 10%.