Development of a novel bipolar stacked Iron/Air Battery Stack

Summary:

Within the scope of the project “ELuStat” an iron/air battery stack is being developed. Both, the iron and the air electrode are subjected for investigation. A battery stack will be designed with the best performing electrodes.
A significant amount of active material in state-of-the-art powder-based iron electrodes cannot be utilized sufficiently. Conventional iron electrodes consist of hot-pressed iron powders. We use an approach to implement sub-micrometer layers of iron via galvanic deposition. Our experiments showed that the capacity can be increased significantly by using this approach. To further increase the surface area and, thus the capacity of the electrode, the iron layer is electroplated on a pre-structured three-dimensional current collector. Furthermore, parasitic hydrogen evolution is being investigated to enhance the poor coulomb efficiency, i.e. by using sulfur-based systems.
State of the art air electrodes contain carbon black as a conductive additive and noble metals as catalyst. Carbon black suffers from corrosion at high potentials (as applied to the electrode during charging). Noble metal catalysts are very expensive and their availability is limited. Promising alternatives are mixed-valent metal oxides which show high electro catalytic activity towards oxygen reduction and –evolution. These oxides are utilized and implemented in an air electrode which is manufactured by hot-pressing. This electrode is carbon-free (nickel based) and PTFE bonded. The whole process is completely dry, hence, excluding environmental harmful solvents.