Exploration of phase diagram, structural and dynamic behavior of [HMG][FSI] mixtures with NaFSI across an extended composition range
Exploration of phase diagram, structural and dynamic behavior of [HMG][FSI] mixtures with NaFSI across an extended composition range
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探索 [HMG][FSI] 与 NaFSI 混合物在扩展组成范围内的相图、结构和动态行为
DOI：
10.1039/d2cp01910h
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发表时间：
2022
影响因子：
3.3
通讯作者：
Forsyth, Maria
中科院分区：
文献类型：
--
作者：
Biernacka, Karolina;Makhlooghiazad, Faezeh;Popov, Ivan;Zhu, Haijin;Chotard, Jean-Noël;O’Dell, Luke A.;Sokolov, Alexei P.;Pringle, Jennifer M.;Forsyth, Maria
六甲基胍双（氟磺酰基）酰亚胺（[HMG][FSI]）是一种新型的固态有机离子塑料晶体，在碱金属电池中具有潜在的应用前景。本研究提供了一个详细的探索[HMG][FSI]混合物的结构和动态行为的钠盐NaFSI在整个组成范围从0到100摩尔%。所有混合物在室温下均为固体。采用差示扫描量热法（DSC）、同步辐射X射线衍射（SXRD）和多核固态NMR光谱的组合来确定部分相图。25摩尔% NaFSI/75摩尔% [HMG][FSI]组合物呈现为低共熔组合物，低共熔转变温度为44 °C。DSC和SXRD都强烈支持在接近50 mol% NaFSI时形成新化合物。有趣的是，一致地发现53摩尔% NaFSI [HMG][FSI]组合物显示出纯化合物的特征，而50摩尔%材料总是显示出第二相。所检查的许多组合物显示出不寻常的亚稳态行为。此外，通过NMR测定的离子动力学表明，对于这些材料，Na+和FSI−阴离子在液态（包括亚稳态）下比HMG阳离子明显更移动的。
Hexamethylguanidinium bis(fluorosulfonyl)imide ([HMG][FSI]) has recently been shown to be a promising solid state organic ionic plastic crystal with potential application in advanced alkali metal batteries. This study provides a detailed exploration of the structural and dynamic behavior of [HMG][FSI] mixtures with the sodium salt NaFSI across the whole composition range from 0 to 100 mol%. All mixtures are solids at room temperature. A combination of differential scanning calorimetry (DSC), synchrotron X-ray diffraction (SXRD) and multinuclear solid state NMR spectroscopy is employed to identify a partial phase diagram. The 25 mol% NaFSI/75 mol% [HMG][FSI] composition presents as the eutectic composition with the eutectic transition temperature at 44 °C. Both DSC and SXRD strongly support the formation of a new compound near 50 mol% NaFSI. Interestingly, the 53 mol% NaFSI [HMG][FSI] composition was consistently found to display features of a pure compound whereas the 50 mol% materials always showed a second phase. Many of the compositions examined showed unusual metastable behaviour. Moreover, the ion dynamics as determined by NMR, indicate that the Na+ and FSI− anions are signifcantly more mobile than the HMG cation in the liquid state (including the metastable state) for these materials.