Department of Chemistry, Oregon State University , Corvallis, Oregon 97331-4003, United States.
Materials Science and Engineering, University of California, Riverside , 900 University Avenue, Riverside, California 92521, United States.
J Am Chem Soc. 2017 Sep 20;139(37):13031-13037. doi: 10.1021/jacs.7b06313. Epub 2017 Sep 8.
We report that crystalline 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), an organic solid, is highly amenable to host divalent metal ions, i.e., Mg and Ca, in aqueous electrolytes, where the van der Waals structure is intrinsically superior in hosting charge-dense ions. We observe that the divalent nature of Mg causes unique squeezing deformation of the electrode structure, where it contracts and expands in different crystallographic directions when hosting the inserted Mg-ions. This phenomenon is revealed experimentally by ex situ X-ray diffraction and transmission electron microscopy, and is investigated theoretically by first-principles calculations. Interestingly, hosting one Mg ion requires the coordination from three PTCDA molecules in adjacent columns of stacked molecules, which rotates the columns, thus reducing the (011) spacing but increasing the (021) spacing. We demonstrate that a PTCDA Mg-ion electrode delivers a reversible capacity of 125 mA h g, which may include a minor contribution of hydronium storage, a good rate capability by retaining 75 mA h g at 500 mA g (or 3.7 C), and a stable cycle life. We also report Ca storage in PTCDA, where a reversible capacity of over 80 mA h g is delivered.
我们报告称，有机固体 3,4,9,10-苝四羧酸二酐（PTCDA）高度适合在水基电解质中容纳二价金属离子，例如 Mg 和 Ca，其中范德华结构在容纳电荷密集离子方面具有内在优势。我们观察到 Mg 的二价性质导致了电极结构的独特挤压变形，当容纳插入的 Mg 离子时，它会在不同的晶体学方向上收缩和扩展。这种现象通过非原位 X 射线衍射和透射电子显微镜实验得到证实，并通过第一性原理计算进行了理论研究。有趣的是，容纳一个 Mg 离子需要来自堆叠分子相邻列中三个 PTCDA 分子的配位，这会导致分子柱旋转，从而减小（011）间距但增加（021）间距。我们证明了 PTCDA-Mg 离子电极具有 125 mA h g 的可逆容量，其中可能包括少量的氢离子储存贡献，在 500 mA g（或 3.7 C）下具有良好的倍率性能，保留了 75 mA h g 的容量，并且具有稳定的循环寿命。我们还报告了在 PTCDA 中储存 Ca 的情况，其中提供了超过 80 mA h g 的可逆容量。
