報告書番号

W02023

タイトル（和文）

MCFC性能表示式の高精度化 -電解質物性に基づくカソード性能推算手法の開発-

タイトル（英文）

Modification of reaction resistance model of MCFCDevelopment of cathode performance estimation method using electrolyte properties based on reaction resistance model

概要 （図表や脚注は「報告書全文」に掲載しております）

溶融炭酸塩形燃料電池の寿命やセル性能の改善のため、電解質である炭酸塩組成の最適化は重要である。炭酸塩組成を変更した場合のセル性能を実験に先だってその物性値のみから推算できれば効率的な最適化が可能となる。そこで、電中研提案の性能表示式の係数と物性値との関係式を基に、任意の炭酸塩組成におけるカソード性能を、物性値のみから推算する手法を開発した。まず、物性値の推算方法を確立し、これを用いて係数と物性値との関係式を検証した結果、これまで気相拡散としてきた抵抗は気体の溶解に対応するものであり、関係式を改良した。さらに、これまで実験により決定していた拡散距離と反応面積との比を電極内の炭酸塩量を支配する毛細管力から推算する手法を開発した。これにより多様な炭酸塩組成を適用した場合のカソード性能を物性値のみから推算することが、初めて可能となり、温度575℃以下ではLi/Na/Kセルが最も電圧が高くなる可能性を明らかにできた。

概要 （英文）

The optimization of composition of molten carbonate as the electrolyte is extremely important to improve cell life and performance of molten carbonate fuel cell. Especially, it is useful to able to estimate cathode performances only with the carbonate properties without cell experiments. Therefore, a cathode performance estimation method has been developed based on a relation equation between coefficients in cathode reaction resistance model and carbonate properties, developed by CRIEPI. The carbonate properties such as diffusion coefficient and Henry’ coefficient are essential to achieve the performance estimation. However, some of these properties were not observed. An estimation method for these properties was developed. Diffusion coefficients and Henry’ coefficients are estimated form other properties such as viscosity. The relation equation was verified with estimated properties. It was found that resistance which was recognized as CO2 gas phase diffusion process is represented by CO2 dissolution process. The relation equation was improved based on electrochemical theory. Furthermore, ratio of diffusion layer and active reaction area which was obtained by experiments is related to capillary force which controls the carbonate distribution in the cathode. As a result, it is possible to estimate a cathode performance with a certain composition of carbonate by this performance estimation method with no experiment. Using the method, cell performances with various compositions of the carbonate were estimated. It was found out that a cell with Li/Na/K carbonate should have the best cell performance at operating temperatures lower than 575 C.

報告者

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