Room temperature fluoride ion conductivity in defective β-KSb1-δF4-3δ polycrystals
Room temperature fluoride ion conductivity in defective β-KSb1-δF4-3δ polycrystals
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DOI：
10.1016/j.jpowsour.2020.229173
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发表时间：
2021-01-31
影响因子：
9.2
通讯作者：
Ikuhara, Yuichi
中科院分区：
文献类型：
--
作者：
Kawahara, Kazuaki;Ishikawa, Ryo;Ikuhara, Yuichi
为了实现氟离子二次电池的室温运行，对快速氟离子导体的研制提出了很高的要求。四氟锑酸钾(KSbF4)是一种空气稳定的晶态F-离子导体，可用液相法合成。考虑到离子导电晶体中晶格缺陷的影响，我们阐明并提出了在熔化温度(550K)以下的热处理在β-KSb1-deltaF4-3(Delta=0.54)中引入了大量的晶格缺陷，从而大大提高了F-离子的电导率。材料的F离子电导率在室温下达到10(-4)S cm(-1)量级，在420K时达到10(-2)S cm(-1)量级，比490K烧结时高出两个数量级。能谱分析表明，在热处理过程中，SbF3从块体中挥发，但保留了晶格骨架，表明Sb(54%)和F(41%)位上的大量空位显著促进了β-KSb1-βF4-3三角洲多晶的氟离子扩散系数。目前的低于熔点的热处理方法应适用于提高复合氟盐的离子导电性。
For a room temperature operation of fluoride ion secondary batteries, it is strongly demanded for a development of fast fluoride ion conductors. Potassium tetrafluoroantimonate (KSbF4) is an air stable crystalline F- ion conductor that can be synthesized by a liquid phase method. Taking account for the effects of lattice defects in ion conductive crystals, we elucidate and propose that a heat treatment just below the melting temperature (550 K) introduces significant amounts of lattice defects in beta-KSb1-delta F4-3 delta (delta = 0.54), which drastically increases the F- ion conductivity. The F- ion conductivity of the material is now reached into the order of 10(-4) S cm(-1) at room temperature and 10(-2) S cm(-1) at 420 K, which are two orders of magnitude higher than those in the sintering at 490 K. Spectroscopic analyses revealed that, during the heat treatment, SbF3 evaporates from the bulk with retaining the lattice framework, suggesting that a number of vacancies at Sb (54%) and F (41%) atomic sites remarkably promote the F- ion diffusivity in beta-KSb1-delta F4-3 delta polycrystals. The present heat treatment method just below the melting point should be applicable to improve the Fion conductivity of complex salt fluorides.