35000

Figure 5 shows history of calculated shorting current density. Short current density began to increase at 1400 h and then gradually increased with operation time. This result agrees-with the measured voltage history in Fig. 4. The shorting current would be caused by NiO cathode dissolution. The measured shorting time shows a good agreement with the time calculated by empirical equation (1). Ni contents of Li/K cells at 1400 h calculated by data of single cells are enough to occur the shorting(6). However, Ni contents of Li/Na cells are lower than of Li/K cells since NiO solubility of Li/Na is lower than of Li/K.

4. Conclusions

• Each cell performance of the stack is able to be analyzed by new performance analysis method with good accuracy.

• Voltage drop by R;r of Li/Na cell is approximately half of that of Li/K cell from the analysis.

• Diffusion of super oxide and C02 plays an important roll in the cathode polarization. It is suggested that thickness of electrolyte film on the cathode of low performance cell is thicker than of high performance cell or that actual effective cell area for cathode reaction of low performance cell is smaller than of high performance cell.

• Shoring by NiO cathode dissolution would take place in Li/K cells at 1400 h. The shorting time agreed with estimated value by empirical equation.

References

(1) Y. Mugikura, T. Abe, S. Yoshioka and H. Urushibata, J. Electrochem. Soc. 142.2971 (1995)

(2) M. Yoshikawa, F. Yoshiba, H. Morita. T. Abe, M. Yamaguchi and K. Iwamoto. The second FCDIC Fuel Cell Symposium Proceedings 289(1995)

(3) Y. Mugikura. H. Morita. Y. Izaki and T. Watanabe. submitted to The 37th Batten-Symposium in Japan (1996)

(4) Y. Mugikura, T. Abe, T. Watanabe and Y. Izaki, Denki Kagaku, 60. 124 (1992)

(5) H. Morita. Y. Mugikura. Y. Izaki, T. Watanabe and T. Abe, Denki Kagaku 63,1053 (1995)

(6) Y. Mugikura, M. Yoshikawa. Y. Izaki and T. Watanabe.. The second International Fuel Cell Conference Proceedings 169 (1996)

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