Untangling the Structure and Dynamics of Lithium-Rich Anti-Perovskites Envisaged as Solid Electrolytes for Batteries
Untangling the Structure and Dynamics of Lithium-Rich Anti-Perovskites Envisaged as Solid Electrolytes for Batteries
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DOI：
10.1021/acs.chemmater.8b02568
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发表时间：
2018-11-27
影响因子：
8.6
通讯作者：
Rettenwander, Daniel
中科院分区：
文献类型：
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作者：
Hanghofer, Isabel;Redhammer, Guenther J.;Rettenwander, Daniel
富锂反钙钛矿（lirap）作为另一种可以实现无易燃液体全固态电池的优异固体电解质，受到了广泛的关注。尽管有几项研究报道了lirap的特性，但许多问题仍未得到解答。特别是，这些包括有关结构、稳定性和锂离子电导率和扩散率的基本问题。此外，目前尚不清楚先前报道的一些化合物是否真的存在。为了弄清lirap的现状，我们合成了“Li3OCl”和Li2OHCl多晶态，并应用了多种方法，如粉末x射线衍射（PXRD）、粉末中子衍射（PND）、核磁共振波谱和阻抗波谱等，对lirap进行了细致的研究。本文自批判地得出结论：由于晶格度量和晶格参数非常相似，两种化合物的立方晶型不能通过PXRD单独区分。此外，PXRD还存在探测H和Li的困难。即使是我们的PND数据的Rietveld精化也被证明是复杂的，并且不容易以一种直接的方式解释。然而，在这里，我们报告了第一个立方结构模型和一个新的正交晶形，也包含了氢原子的结构信息。将“Li3OCl”暴露于空气中的原位PXRD显示，Li3OCl快速降解为Li2CO3和无定形LiCl中心点xH(2)O。最有可能的是，“Li3OCl”的不稳定性解释了早期关于异常高离子导电性的发现，因为分解产物LiCl中心点xH(2)O提供了足够好的导电性，适用于某些应用，当然，不包括那些需要非质子条件或无任何水分电解质的应用。考虑到“无h - Li3OCl”以及Li-5(OH)(3)Cl-2、Li-5(OH)(2)Cl-3、Li-3(OH)(2)Cl -3和Li-3(OH)Cl-2，我们相信Li-4(OH)(3)Cl和Li3-x(OHx)Cl的变体，其中x > 0，从实用的角度来看，是迄今为止唯一稳定的富锂反钙钛矿。
Lithium-rich anti-perovskites (LiRAPs) have attracted a great deal of attention as they have been praised as another superior group of solid electrolytes that can be used to realize all-solid-state batteries free of flammable liquids. Despite several studies that have reported on the properties of LiRAPs, many questions remain unanswered. In particular, these include fundamental ones concerning the structure, stability, and Li-ion conductivity and diffusivity. Moreover, it is not clear whether some of the previously reported compounds do really exist. To untangle the current picture of LiRAPs, we synthesized "Li3OCl" and Li2OHCl polymorphs and applied a wide spectrum of methods, such as powder X-ray diffraction (PXRD), powder neutron diffraction (PND), nuclear magnetic resonance spectroscopy, and impedance spectroscopy to carefully shed some light on LiRAPs. Here we self-critically conclude that the cubic polymorph of the two compounds cannot be easily distinguished by PXRD alone as the lattice metrics and the lattice parameters are very similar. Furthermore, PXRD suffers from the difficulty of detecting H and Li. Even Rietveld refinement of our PND data turned out to be complicated and not easily interpreted in a straightforward way. Nevertheless, here we report the first structural models for the cubic and a new orthorhombic polymorph containing also structural information about the H atoms. In situ PXRD of "Li3OCl", intentionally exposed to air, revealed rapid degradation into Li2CO3 and amorphous LiCl center dot xH(2)O. Most likely, the instability of "Li3OCl" explains earlier findings about the unusually high ion conductivities as the decomposition product LiCl center dot xH(2)O offers an electrical conductivity that is good enough for some applications, excluding, of course, those that need aprotic conditions or electrolytes free of any moisture. Considering "H-free Li3OCl" as well as Li-5(OH)(3)Cl-2, Li-5(OH)(2)Cl-3, Li-3(OH)(2)Cl, and Li-3(OH)Cl-2, we are confident that Li-4(OH)(3)Cl and variants of Li3-x(OHx)Cl, where x > 0, are, from a practical point of view, so far the only stable lithium-rich anti-perovskites.