Elucidation of the electrolyte volatile phenomenon of MCFC by the visualization technique

熔盐的挥发是影响熔融碳酸盐燃料电池（MCFC）性能的因素之一。由于MCFC长时间运行导致电解液耗竭，电解液挥发物堵塞排气管，导致MCFC功率下降。然而，尽管这是一个严重的问题，但大多数研究者对这一问题并不感兴趣。其中一个原因是碳酸盐的碱性很强，分析起来比较困难。因此，我们提出了一种通过非接触式图像测量技术来观察电池中电解质挥发现象的方法。我们使用MCFC单细胞框架，它有一个观察窗和一个照射窗。结果阐明了(Li+K)/CO_3的挥发现象。阳极(Li+K)/CO_3的挥发分通过细胞反应产生，而阴极(Li+K)/CO_3的挥发分几乎不通过细胞反应产生。此外，我们还阐明了(Li+Na)/CO_3的电解液挥发现象。虽然不能观察到与细胞反应有关的挥发物，但有时可以证实与细胞反应无关的挥发物。一般来说，(Li+Na)/CO_3电解液比(Li+K)/CO_3电解液挥发性差。在电池工作状态下，采用非接触式图像测量技术对电池内部进行了观察，证实了(Li+Na)/CO_3电解质的优越性。然而，大量源自湿密封部分泄漏的电解质在运行后立即排放，并持续到大约一周后的锂/钠电解质上。因此，由于Li/Na电解质很难渗透到电极的孔隙中，应避免电极与分离器间隙装配精度差、电解液过充和启动后立即流量大。

Volatilization of molten salt is one of the factors to control the performance of Molten Carbonate Fuel Cells (MCFC). The power of MCFC deteriorates for which the long time operation of MCFC causes the depletion of the electrolyte and this electrolyte volatile matter blocks exhaust pipe. However, most researchers are not interested in this problem in spite of serious problem. One of the reasons is that it is difficult to analyze it because the carbonate is strong alkalinity. Therefore, we proposed the method by which an electrolyte volatile phenomenon in the cell can be observed by a non-contact image measurement technique. We use MCFC single cell's frame which has an observation window and an irradiation window. As a result, we elucidate the volatile phenomenon of (Li+K)/CO_3. Although the volatile matters of (Li+K)/CO_3 in anode are produced with a cellular reaction, (Li+K)/CO_3 in cathode is hardly volatiled with cell reaction. Moreover, we elucidate the electrolyte volatile phenomenon of (Li+Na)/CO_3. Although the volatile matter with cell reaction cannot be observed, the volatile matter which does not depend on the cell reaction was sometimes confirmed. Generally, (Li+Na)/CO_3 electrolyte is hardly volatile more than (Li+K)/CO_3 electrolyte. We confirmed the advantage of (Li+Na)/CO_3 electrolyte by observing the inside cell by a non-contact image measurement technique under the cell operating condition. However, a large amount of electrolytes that originated in the leakage from the wet seal part are discharged beginning immediately after operation and lasting until about one week later on the Li/Na electrolyte. Therefore, because the Li/Na electrolyte hardly permeates into the pores of an electrode, a poor assembly accuracy of the gap between an electrode and a separator, an overfilling of electrolyte and a large flow-rate immediately after start-up should be avoided.