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

熔盐的挥发是控制熔融碳酸盐燃料电池（MCFC）性能的因素之一。 MCFC的功率下降，MCFC长时间运行导致电解液耗尽，电解液挥发物堵塞排气管。然而，尽管问题很严重，但大多数研究人员对这个问题并不感兴趣。原因之一是碳酸盐呈强碱性，分析起来比较困难。因此，我们提出了通过非接触式图像测量技术来观察电池内电解质挥发现象的方法。我们使用MCFC单电池的框架，其具有观察窗和照射窗。由此，我们阐明了(Li K)/CO_3的挥发现象。尽管阳极中的(LiK)/CO_3的挥发物是通过电池反应产生的，但阴极中的(LiK)/CO_3几乎不随电池反应而挥发。此外，我们还阐明了(Li Na)/CO_3的电解液挥发现象。虽然无法观察到伴随细胞反应的挥发物，但有时也能够确认不依赖于细胞反应的挥发物。一般来说，(Li Na)/CO_3电解液比(Li K)/CO_3电解液不易挥发。我们通过非接触式图像测量技术在电池运行条件下观察电池内部，证实了(Li Na)/CO_3电解质的优势。然而，在Li/Na电解液上，由于湿密封部分泄漏而产生的大量电解液在操作后立即开始排出，并持续到大约一周后。因此，由于Li/Na电解液很难渗透到电极的孔隙中，因此应避免电极与隔膜之间的间隙装配精度差、电解液过量填充以及启动后立即大流量。

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.