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| Home > Publications database > A first prototype of high-temperature rechargeable oxide batteries (ROB) with iron-based storage material |
| Conference Presentation (After Call) | FZJ-2015-05005 |
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2015
Abstract: The present investigation describes the results of a kinetic study of porous storage material for a novel high-temperature rechargeable oxide battery (ROB). The new planar battery design consists of a regenerative solid oxide cell and a storage redox unit with a stagnant hydrogen/steam atmosphere and embedded porous Fe-based material which has to provide high oxygen-ion storage capacity, good reaction kinetics and long-term stability.During long-term exposure in the alternating redox atmosphere at 800 °C, the structure of the storage material shows degradation effects like structural coarsening and outward iron diffusion, thus making the storage element incapable of storing the required amount of oxygen during continuous operation of the rechargeable battery. The porous Fe/Fe-oxide storage material is therefore supported by inert or reactive oxides. Addition of inert oxides (e.g. ZrO2) in sufficient amount reduces the microstructural degradation, however results in a substantial decrease in storage capacity. Among the added oxides forming mixed oxides with Fe in the relevant oxygen partial pressure range of ~ 10-18 – 10-20 bar, the most promising results were obtained with additions of MgO and CaO. During the oxidation step these oxides form mixed oxides with Fe oxide which in turn change composition during the reduction step. In this way a framework is obtained which reduces sintering and outward Fe migration in the storage component.In addition to these studies, supplementary research of the iron-based storage material was carried out aiming at microstructural optimization of porosity and powder morphology. Also, more feasible manufacturing methods such as tape casting and extrusion were successfully implemented for production of storage elements. The storage materials with the best results regarding capacity, efficiency, and lifetime were used during pilot battery testing to examine material behavior under real operating conditions, showing ~ 200 full charge-discharge cycles of up to 70 minutes each with a current density of 150 mA/cm2.
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