Iron-Air Battery Operating at High Temperature

A simple configuration for an Fe-air rechargeable battery operating at high temperature was investigated. Two different ceramic electrolytes, that is, gadolinia-doped ceria (CGO) and strontium/magnesium-doped lanthanum gallate (LSGM), were studied. Strontium-doped lanthanum ferrite-cobaltite (LSFCO) perovskite was used as the air electrode, whereas an Fe0/Fe2O3-CGO composite was used as the Fe electrode. The synthesized CGO and LSGM supporting electrolytes were characterized by proper ionic conductivity for this application (7.4×10-2 S cm-1 at 800 °C). The LSFCO perovskite electrode showed excellent reversibility in symmetrical cells. Low overpotentials were recorded for the evolution of oxygen (0.1 V at 1.7 A cm-2) and the oxygen reduction process (0.1 V at 2.4 A cm-2) at 800 °C. The high-temperature battery based on the CGO electrolyte showed a pronounced propensity to spontaneously discharge. This was caused by redox behavior involving the interconversion between the Ce4+ and Ce3+ ions in the crystallographic structure, which caused a parasitic electron drag through the electrolyte. On the other hand, the LSGM-based battery showed promising cyclability characteristics at 800 °C with an open-circuit voltage higher than 1 V, an electric capacity of 0.3 Ah g-1, and an energy density of 0.22 Wh g-1. However, significant improvements in the coulombic efficiency (?42 %) for this battery system are necessary for practical applications.