報告書番号

W16

タイトル（和文）

Li/Na系電解質ＭＣＦＣスタックの実用化

タイトル（英文）

Development of Practical Molten Carbonate Fuel Cell Stack Applying Li/Na Carbonate Electorolyte

概要 （図表や脚注は「報告書全文」に掲載しております）

MCFCの電解質に関する探索の結果Li/Na系電解質を選定し、プレスセパレータと組み合わせることによって、以下の成果を得た。・Li/Na系電解質セルでは圧力ゲインが大きく、加圧下でLi/K系セルと同等の電圧が得られると共に、Ni短絡発生時間も倍増できた。・Li/Na比、カソード電極構造、集電板防食対策などを適正化することにより、Li/K系セルを上回る性能を得た。・プレスセパレータと組み合わせた10kW級スタックを試作し、基本特性試験を行った結果、最大出力密度として2.5kW/m2を達成し、低コスト化に向けての対応が可能であることも明らかとした。・さらに、電解質板の改良、温度管理技術の高度化を行い、10,000時間に亘る寿命特性を検証した。電圧低下率はこれまで試験したスタックの中で最も小さい値(0.3%/1000時間）を示し、実用化のための目標値をほぼ達成することができた。

概要 （英文）

From investigations on characteristics of several carbonate electrolyte, Li/Na had been selected as a promissing MCFC carbonate. Pressure gains of Li/Na carbonate cell was more than Li/K carbonate cell, and Ni shortening time of Li/Na cell exceeded the Ni shortning time of Li/K carbonate cell. By optimization on the ratio of Li and Na, on cathode structure, and on installing procedure of Li/Na carbonate cell, the performance of Li/Na cell surpassed the performance of Li/K carbonate cell. 10kW class MCFC stacks applying Li/Na carbonate electrolyte with press stamping separator, which have a reactive area of 0.44m2 and 1.03 m2, has been developed and many tests had been carried out. In the initial tests, observed cell voltages of 0.44m2-10kW-class stack agreed with the voltage predicted from the 100cm2 bench scale cell test results. The agreement proves the installing procedure of the bench scale cell can be applied to the 0.44m2-10kW-class stacks.In the high current density operating tests of 0.44m2- 10kW-class stack, the electrical power density of 2.46kW/m2 had been recorded at the operating current density of 3000A/m2. In the endurance test of 0.44m2-10kW-class stack, however, unexpected shortening had occurred during the operating time of 2500-4500 hours, which is caused by a defective formation of the matrix of electrolyte. The shortening seems to be caused by the crack occurred in the electrolyte matrix. The voltage degradation rate of 0.44m2 ‐10kW-class stack was 0.52% over 1000 hours, which result leads that the matrix was insufficient for the long life time of MCFC stack.Final endurance test had carried out with the 1.03m2-10kW-class stack, which matrix had been revised. The fuel utilisation and the leakage of anode gas never changed during 10,000 hours operating test; this result suggests no shortening occurred in the 10,000 hours endurance test. The cell voltage degradation rate was around 0.2-0.3% over 1000 hours in 1.03m2-10kW-class stack. From the comparison of the stack performance of 0.44m2- and 1.03m2- 10kW-class stack under the same operating condition, the performance of 1.03m2- stack was lower at the beginning of the endurance test, however, its performance had exceeded the performance of 0.44m2-10kW-class stack during the 10,000 hours operating test. By carrying out of the high current density operating test and 10,000 hours endurance test using the commercial size 10kW-class stacks, the stability of the MCFC stack having Li/Na carbonate electrolyte with press stamping separator had been proved.

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