Abstract Scope |
Freeze-casting is a low-cost, scalable processing method capable of producing porous lamellar structures with an ideal morphology for gas reactions. The multiple oxidation states, low cost, and availability of iron oxide make it an attractive material for energy storage via redox cycling. However, the practicality of iron-based energy storage structures, such as iron-steam batteries, is limited by the high volumetric expansion incurred as metallic Fe transforms to Fe3O4, which leads to rapid densification and lack of gas access in traditional Fe/Fe3O4 powder beds. Freeze-cast structures can mitigate this deleterious effect via built-in expansion volume that allows for cyclic expansion/contraction while still allowing gas flow throughout the sample. We present recent advances in these structures by freeze-casting blends of iron oxide powders paired with either nickel-, cobalt-, or molybdenum oxide. These mixed-powder systems lend the structure additional strength and toughness during cycling, showing promise for long-term energy storage via redox cycling. |