Electrochemical investigation of the P2-NaxCoO2 phase diagram
Electrochemical investigation of the P2-NaxCoO2 phase diagram
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DOI：
10.1038/nmat2920
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发表时间：
2011-01-01
期刊：
影响因子：
41.2
通讯作者：
Delmas, C.
中科院分区：
文献类型：
--
作者：
Berthelot, R.;Carlier, D.;Delmas, C.
钠层状氧化物NaxCoO（2）形成最迷人的低维和强关联系统之一;特别是P2-NaxCoO2表现出各种单相域，根据钠浓度的不同，具有不同的Na +/空位模式。在这里，我们使用钠电池来清楚地描绘x>= 0.50的P2-NaxCoO（2）相图。通过耦合的电化学过程与原位X射线衍射实验，我们确定了连续的单相或两相域上出现的钠插层与一个相当好的精度相比，与以前的研究。我们报告了新的单相域，我们强调了一些有序相的热不稳定性，从电化学研究在不同温度下。由于每个相的特征在于其费米能级相对于Na +/Na电对的位置，我们表明，即使是大量的每种材料的合成，也可以通过电化学进行。对所制备的Na1/2CoO2和Na2/3CoO2有序相的物理性能进行了表征和比较。电化学过程被证实是一种精确的路线，以连续的方式精确地研究这样一个复杂的系统，并提供了一种新的方法来合成具有非常窄的存在范围的材料。
Sodium layered oxides NaxCoO(2) form one of the most fascinating low-dimensional and strongly correlated systems; in particular P2-NaxCoO2 exhibits various single-phase domains with different Na+/vacancy patterns depending on the sodium concentration. Here we used sodium batteries to clearly depict the P2-NaxCoO(2) phase diagram for x >= 0.50. By coupling the electrochemical process with an in situ X-ray diffraction experiment, we identified the succession of single-phase or two-phase domains appearing on sodium intercalation with a rather good accuracy compared with previous studies. We reported new single-phase domains and we underlined the thermal instability of some ordered phases from an electrochemical study at various temperatures. As each phase is characterized by the position of its Fermi level versus the Na+/Na couple, we showed that the synthesis of each material, even in large amounts, can be carried out electrochemically. The physical properties of the as-prepared Na1/2CoO2 and Na2/3CoO2 ordered phases were characterized and compared. Electrochemical processes are confirmed to be an accurate route to precisely investigate in a continuous way such a complex system and provide a new way to synthesize materials with a very narrow existence range.