In recent years a renewed interest in developing metal air batteries has arisen, driven by the advances in nanomaterials research that could bring metal air batteries closer to their theoretical specific energy density. For the particular case of the iron-air battery a theoretical energy density of 764 W h kg^-1 in combination with the abundance, low cost, eco-friendliness, recyclability, non-toxicity of the materials, and the possibility to work as a secondary battery makes this electrochemical system appealing to develop [1].

Nevertheless, there are several challenges that requires to be improved such as the development of a high efficient iron electrode formulation that reduces the amount of parasitic hydrogen evolution during charge, with a highly porous structure; the development of a good performing bifunctional gas diffusion electrode [2] and the design of a lightweight battery cell design that reduces ohmic losses, electrolyte leaks, allow sufficient air supply to the gas diffusion electrodes and allows evolved gas to be vented [3].

More particular challenges related to the performance of the iron electrodes includes the passivation of the iron electrode at high discharge rates and the low faradaic efficiency due to the parasitic H2 evolution that takes places during the charging process. The engineering of the electrodes in an efficient way to avoid adding extra weight and a way to efficiently supply air are challenging engineering design aspects that have to be addressed to achieve a new level of development.

In this work, the individual iron and air electrodes performance in half-cell configurations will be presented (Fig1) together with a comparison between various iron electrode formulations and some considerations about the engineering design of an iron air battery using additive manufacturing.

References

1. R. D. McKerracher, C. Ponce de Leon, R. G. A. Wills, A. A. Shah, and F. C. Walsh, “A Review of the Iron–Air Secondary Battery for Energy Storage,” Chempluschem, vol. 80, no. 2, pp. 323–335, 2015.
2. R. D. McKerracher, H. A. Figueredo-Rodríguez, C. Ponce de León, C. Alegre, V. Baglio, A. S. Aricò, and F. C. Walsh, “A high-performance, bifunctional oxygen electrode catalysed with palladium and nickel-iron hexacyanoferrate,” Electrochim. Acta, vol. 206, pp. 127–133, Jul. 2016.
3. H. A. Figueredo-Rodríguez, R. D. McKerracher, C. Ponce de León, and F. C. Walsh, “Current distribution in a rectangular flow channel manufactured by 3-D printing,” AIChE J., Aug. 2016.