Saito Yuria, Umecky Tatsuya, Niwa Junichi, Sakai Tetsuo, Maeda Seiji
National Institute of Advanced Industrial Science and Technology, 1-8-31, Midorigaoka, Ikeda, Osaka, Japan.
J Phys Chem B. 2007 Oct 11;111(40):11794-802. doi: 10.1021/jp072998r. Epub 2007 Sep 15.
Ionization conditions of each ionic species in lithium ionic liquid electrolytes, LiTFSI/BMI-TFSI and LiTFSI/BDMI-TFSI, were confirmed based on the diffusion coefficients of the species measured by the pulsed gradient spin-echo (PGSE) NMR technique. We found that the diffusion coefficient ratios of the cation and anion species D(Li)(obs)/D(F)(obs) of the lithium salt and D(H)(obs)/D(F)(obs) of the ionic liquid solvent were effective guides to evaluate the ionization condition responsible for their mobility. Lithium ions were found to be stabilized, forming the solvated species as Li(TFSI)3(2-). TFSI- anion coordination could be relaxed by the dispersion of silica to form a gel electrolyte, LiTFSI/BDMI-TFSI/silica. It is expected that the oxygen sites on the silica directly attract Li+, releasing the TFSI- coordination. The lithium species, loosing TFSI- anions, kept a random walk feature in the gel without the diffusion restriction attributed from the strong chemical and morphological effect as that in the gel with the polymer. We can conclude that the silica dispersion is a significant approach to provide the appropriate lithium ion condition as a charge-transporting species in the ionic liquid electrolytes.
基于通过脉冲梯度自旋回波（PGSE）核磁共振技术测量的各离子物种的扩散系数，确定了锂盐离子液体电解质LiTFSI/BMI-TFSI和LiTFSI/BDMI-TFSI中各离子物种的电离条件。我们发现，锂盐阳离子与阴离子物种的扩散系数比D(Li)(obs)/D(F)(obs)以及离子液体溶剂的D(H)(obs)/D(F)(obs)是评估影响其迁移率的电离条件的有效指标。研究发现锂离子得以稳定，形成溶剂化物种Li(TFSI)3(2-)。通过二氧化硅的分散作用可使TFSI-阴离子配位作用减弱，从而形成凝胶电解质LiTFSI/BDMI-TFSI/二氧化硅。预计二氧化硅上的氧位点会直接吸引Li+，从而解除TFSI-配位作用。失去TFSI-阴离子的锂物种在凝胶中保持随机游走特征，不存在像聚合物凝胶那样因强烈化学和形态效应而产生的扩散限制。我们可以得出结论，二氧化硅分散是在离子液体电解质中提供合适锂离子条件作为电荷传输物种的一种重要方法。
