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首页> 外文期刊>Materials Science and Engineering >Overall conductivity and NCL-type relaxation behavior in nanocrystalline sodium peroxide Na_2O_2-Consequences for Na-oxygen batteries
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Overall conductivity and NCL-type relaxation behavior in nanocrystalline sodium peroxide Na_2O_2-Consequences for Na-oxygen batteries

机译：纳米晶过氧化钠Na_2O_2的整体电导率和NCL型弛豫行为-氧电池的后果

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摘要

Metal air batteries are considered as promising candidates for room-temperature batteries with high-energy densities. On discharge, atmospheric oxygen is reduced at the positive electrode which, in the ideal case, forms the discharge products in a reversible cell reaction. In Na-O_2 batteries upon discharge either sodium peroxide (Na_2O_2) or sodium superoxide (NaO_2) is reported to be formed. So far, the charge carrier transport remains relatively unexplored but is expected to crucially determine the efficiency of such energy storage systems. Na_2O_2 is predicted to be an electrical insulator wherein the transport presumably is determined by very slow hopping processes. Understanding the basic fundamental properties of the overall charge carrier transport, including also nanostructured forms of Na_2O_2, is key to developing high-energy metal oxygen batteries. The present study answers the question how overall, i.e., total, conductivity changes when going from microcrystalline to nanocrystalline, defect-rich Na_2O_2. Nanocrystalline Na_2O_2 was prepared via a top-down approach, viz by high-energy ball milling. Milling does not only shrink the average crystallite diameter but also introduces a large amount of defects which are anticipated to influence total conductivity. It turned out that even after vigorous mechanical treatment the conductivity of the sample is only increased by ca. one order of magnitude. The activation energy remains almost untouched. Thus, the increase seen might be attributed to an enhanced number of charge carriers. Low-temperature data reveals nearly constant loss relaxation behavior which has frequently explained in terms of strictly localized electrical relaxation processes.
机译：金属空气电池被认为是具有高能量密度的室温电池的有希望的候选者。放电时，正极上的大气氧被还原，在理想情况下，这在可逆电池反应中形成放电产物。在Na-O_2电池中，放电时会形成过氧化钠（Na_2O_2）或过氧化钠（NaO_2）。迄今为止，电荷载流子的运输仍然相对未被探索，但是有望决定性地确定这种储能系统的效率。 Na_2O_2被认为是电绝缘体，其传输大概是由非常缓慢的跳跃过程决定的。了解整个电荷载流子传输的基本基本特性，包括Na_2O_2的纳米结构形式，对开发高能金属氧电池至关重要。本研究回答了以下问题：从微晶到富含缺陷的纳米晶Na_2O_2时，总的电导率（即总电导率）如何变化。通过自上而下的方法，即通过高能球磨，制备了纳米晶体Na_2O_2。研磨不仅会收缩平均微晶直径，而且会引入大量缺陷，这些缺陷预计会影响总导电率。事实证明，即使经过严格的机械处理，样品的电导率也仅增加了约。一个数量级。活化能几乎保持不变。因此，看到的增加可能归因于电荷载流子数量的增加。低温数据揭示了几乎恒定的损耗弛豫行为，这在严格的局部电弛豫过程方面经常得到解释。

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  • 来源
    《Materials Science and Engineering》 |2016年第9期|85-93|共9页
  • 作者

    Andreas Dunst; Michael Sternad; Martin Wilkening;

  • 作者单位

    Christian-Doppler Laboratory for Lithium Batteries, and DFG FOR 1277, Graz University of Technology, Institute for Chemistry and Technology of Materials, NAWI Graz, Stremayrgasse 9, A-8010 Graz, Austria;

    Christian-Doppler Laboratory for Lithium Batteries, and DFG FOR 1277, Graz University of Technology, Institute for Chemistry and Technology of Materials, NAWI Graz, Stremayrgasse 9, A-8010 Graz, Austria;

    Christian-Doppler Laboratory for Lithium Batteries, and DFG FOR 1277, Graz University of Technology, Institute for Chemistry and Technology of Materials, NAWI Graz, Stremayrgasse 9, A-8010 Graz, Austria;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Impedance spectroscopy; Conductivity; Transport properties; High-energy ball milling;

    机译：阻抗谱;电导率运输特性;高能球磨;

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