Refractory Alloyed Iron-based Redox Active Foams for Iron-Air Batteries

NU 2022-100

INVENTORS
David Dunand*
Jacob Mack 
Samuel Pennell 

SHORT DESCRIPTION 
A fabrication process for iron-molybdenum foam that enhances porosity and allows repeated redox cycling for a high efficiency iron-air battery or hydrogen storage

ABSTRACT
Northwestern researchers have developed a fabrication process using water-based directional freeze casting to manufacture a porous, metallic surface. This unique surface composition is advantageous because it allows increased capacity for repeated uses. Previous iterations of similar technologies see a rapid decline in efficiency after multiple uses that the current technology addresses, expanding the usefulness of iron-air redox reactions for energy storage or generation of hydrogen for downstream applications. In this process, an iron-molybdenum (Fe-25Mo) lamellae is synthesized that has gas-flow chambers and space to accommodate volumetric changes following oxidation. The specific composition additionally inhibits sintering, extending the life cycle of the system by preventing internal damage to the system. Taken together, the presented technology addresses limiting factors of the iron-air redox system, ensuring high capacitance and a reduced propensity for densification. The technological innovations allow increased efficiency of the system by accounting for both expansions and the chemical components as well as the accumulation of rust due to redox reactions. These features allow the iron-air redox system to be repeatedly used at a high capacitance, permitting inexpensive storage for electricity or hydrogen. Furthermore, the system can be applied to situations requiring reversible energy storage as a battery. 

APPLICATIONS  

• Solid-oxide iron-air flow batteries (reversible, multi cycles) 
• Hydrogen generator (water splitting) 
• Hydrogen storage

ADVANTAGES 

• Inexpensive, non-toxic, and earth-abundant materials  
• Scalable processing technique 
• Clean processing (water carrier and sintering) 
• Increased capacity for repeated use 

PUBLICATION
Thesis for Bachelor of Science Honors:  Mack J, Dunand D (2022) “Structural stabilization of Fe-based freeze-cast foams during redox cycling via elemental alloying.”

IP STATUS
A provisional has been filed. 

SEM images of lamellae cross sections indicate that Fe-25Mo maintains interlamellar porosity across multiple consecutive redox cycles. The above figure indicates an increased capacity for extended reuse as the architecture is more permissive to expansion following oxidation.