유효면적이 100㎠인 단위전지의 장기운전을 통하여 용융탄산염 연료전지 운전시 발생하는 Ni-Cr anode의 구조적 변화 및 구성요소간의 전해질 재분포가 전지성능에 미치는 영향을 살펴보았다. Anode로는 환원분위기 하에서 700℃ 및 1,000℃로 30분간 소성한 두 종류의 Ni+10w/oCr을 사용하였다. 1,000℃에서 소성하여 소결 및 creep 저항성이 우수하고 미세기공의 형성이 적은 anode를 사용한 경우 5,200시간 동안 장기운전할 수 있었으며 이때 전지성능에는 큰 감소가 없었다. 즉, 전류밀도 150mA/㎠에서의 전지성능은 초기에 0.83V, 5,200시간 후에 0.77V로서 이 기간 동안의 평균 전지성능 저하율은 약 11.5mV/1,000hr로 나타났다. 그러나 700℃에서 소성한 anode를 사용한 경우에는 800시간 부근에서 급격히 전지성능이 저하되었다. 이것은 anode가 낮은 온도에서 소성되었기 때문에 Cr이 Ni상으로 거의 고용되지 않음으로써 소결 및 creep에 의한 구조적 변형이 야기되었기 때문이며 또한 고용되지 못한 대부분의 Cr 또는 Cr₂O₃가 Lithiation 반응에 의해 LiCrO₂를 생성시킬 때 다량의 미세기공이 형성됨으로써 matrix내의 전해질이 anode쪽으로 이동되어 matrix내에 전해질이 부족해졌기 때문이다.

The effect of the structural change of the Ni-Cr anode and the electrolyte re-distribution among the components during the MCFC operation upon the change in the cell performance was investigated through a long-term operation using the single cell with an effective electrode area of 100cm². Two types of Ni+10w/oCr anode, which were fired at 700℃ and 1,000℃ for 30 minutes under the reduction atmosphere, have been used. The single cell with the anode fired at 1,000℃, showing good resistance to sintering and creep and less formation of micro-pores, was successfully operated for 5,200 hours with no significant decay of the cell performance. The performance of the cell at the current density of 150mA/cm² was 0.83V at the beginning and 0.77V at the operation time of 5,200 hours, and the average decay rate of the cell performance during the operation was about 11.5mV/1,000hr. In the single cell operation using the anode fired at 700℃, however, the rapid degradation of the performance was observed at the operation time of 800 hours. This was because the structural changes of the anode occurred due to sintering and creep, which resulted from a small amount of Cr solid solution in the Ni phase because of low firing temperature. It was also because the lithiation of Cr or Cr₂O₃ of the anode into LiCrO₂ formed so large amount of micro-pores as to redistribute the electrolyte from the matrix to the anode, resulting in the deficiency of the electrolyte in the matrix.

MCFC Anode Electrolyte Redistribution Sintering and Creep

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