Lithium Salt Diffusion in Diblock Copolymer Electrolyte Using Fourier Transform Infrared Spectroscopy.
Lithium Salt Diffusion in Diblock Copolymer Electrolyte Using Fourier Transform Infrared Spectroscopy.
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DOI：
10.1021/acs.jpcb.9b11446
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发表时间：
2020-02
期刊：
影响因子：
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通讯作者：
Kyoungmin Kim;D. Hallinan
中科院分区：
文献类型：
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作者：
Kyoungmin Kim;D. Hallinan
用振动光谱法研究了锂盐在二嵌段共聚物电解质中的扩散。将双三氟甲基磺酰亚胺锂（LiTFSI）溶解在不同浓度（0 - 4.51 molLiTFSI/kgPEO）的层状结构、高分子量聚苯乙烯-聚（环氧乙烷）二嵌段共聚物中。利用时间分辨傅里叶变换红外光谱衰减全反射（FTIR-ATR）测定了盐浓度对LiTFSI扩散系数的影响。利用比尔-朗伯定律，FTIR-ATR检测浓度变化。通过使两种不同盐浓度的聚合物电解质膜接触来驱动相互扩散。因此，在不受电场和电极界面影响的情况下，得到了相互扩散系数。通过与电化学电池中测量的扩散系数进行比较，验证了简单实验方法和直接分析的准确性。两种方法得到的锂盐相互扩散系数仅弱（非单调）依赖于盐浓度。光谱显示存在两种不同解离态的盐族。这可以解释观察到的盐的相互扩散系数的非单调浓度依赖性。这一假设将在未来的工作中通过补充测量进行定量检验。
Diffusion of a lithium salt through a diblock copolymer electrolyte was studied using vibrational spectroscopy. Lithium bis-trifluoromethylsulfonimide (LiTFSI) was dissolved in a lamellar-structured, high-molecular-weight polystyrene-poly(ethylene oxide) diblock copolymer at various concentrations (0 - 4.51 molLiTFSI/kgPEO). The diffusion coefficient of LiTFSI was determined from time-resolved Fourier Transform infrared spectroscopy attenuated total reflectance (FTIR-ATR) as a function of the salt concentration. By applying the Beer-Lambert law, FTIR-ATR was used to detect concentration changes. Mutual diffusion was driven by putting in contact two polymer electrolyte membranes with different salt concentrations. Thus, mutual diffusion coefficients were obtained without the influence of electric fields or electrode interfaces. The accuracy of the simple experimental approach and straightforward analysis were validated by comparison to diffusion coefficients reported from measurements in electrochemical cells. Both methods yield mutual diffusion coefficients of lithium salt that are only weakly (and non-monotonically) dependent on salt concentration. There is some indication in the spectra that there exist two populations of salt with different dissociation states. This could explain the observed non-monotonic concentration dependence of the mutual diffusion coefficient of the salt. This hypothesis will be examined quantitatively with complementary measurements in future work.