Revealing the Correlation between the Solvation Structures and the Transport Properties of Water-in-Salt Electrolytes
Revealing the Correlation between the Solvation Structures and the Transport Properties of Water-in-Salt Electrolytes
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DOI：
10.1021/acs.chemmater.2c03654
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发表时间：
2023-02
影响因子：
8.6
通讯作者：
Xinyi Liu;Shao-Chun Lee;Soenke Seifert;Lilin He;Changwoo Do;R. Winans;Gihan Kwon;Y. Z;Tao Li
中科院分区：
文献类型：
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作者：
Xinyi Liu;Shao-Chun Lee;Soenke Seifert;Lilin He;Changwoo Do;R. Winans;Gihan Kwon;Y. Z;Tao Li
含有21米锂二（三氟甲烷磺酰）亚胺（LiTFSI）的盐中水（WIS）电解质被认为是锂离子电池中使用的常见有机电解质的安全和环保替代品。然而，这些材料的溶剂化结构和输运性质之间的关系仍然是难以捉摸的。在此，我们进行了小角x射线散射（SAXS），小角中子散射（SANS）和x射线对分布函数（PDF）测量LiTFSI水溶液在宽浓度范围内。结合分子动力学模拟，从长尺度到短尺度详细解析了溶剂化结构。研究发现，tfsi溶剂化结构由tfsi溶剂化结构和tfsi网络组成；前者对应溶剂分离离子对，后者对应接触离子对和正阴离子聚集。此外，我们发现与阴离子网络结构相关的qrange弛豫时间表现出与粘度相同的浓度依赖性。结合实验和模拟结果，本研究揭示了LiTFSI的溶剂化结构与溶液的输运性质之间的相关性，这对于理解亚胺基锂离子盐水溶液电解质的输运性质与离子动力学之间的关系至关重要。
Water-in-salt (WIS) electrolytes containing 21 m lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) have been considered as a safe and environment-friendly alternative to common organic electrolytes used in lithium-ion batteries. However, the relation between the solvation structures and transport properties of these materials remains elusive. Herein, we performed small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS), and X-ray pair distribution function (PDF) measurements of LiTFSI aqueous solutions at a wide range of concentrations. Combined with molecular dynamics simulations, the detailed solvation structures from long to short length scale were resolved. We found that the TFSI–solvation structures consist of TFSI–solvated structures and TFSI–networks; the former corresponds to solvent separated ion pairs, while the latter corresponds to contact ion pairs and cation–anion aggregates. In addition, we found that the relaxation time in theqrange associated with the anion network structure exhibits the same concentration dependence as the viscosity. By combining the results from the experiments and simulations, this study revealed a correlation between the solvation structures of LiTFSI and the transport properties of the solutions, which is critical to understand the relation between the transport properties and the dynamics of the ions for imide-based lithium-ion salt aqueous electrolytes.