In recent years, binary transition metal oxides such as magnetite, Fe₃O₄, zinc ferrite, ZnFe₂O₄, magnesium ferrite, MgFe₂O₄ and copper ferrite, CuFe­₂O₄, have gained significant attention as prospective electrodes for lithium based batteries. These materials hold interest due to the low cost iron center, their low environmental impact, and in particular for their high theoretical capacities. Through a combined insertion and conversion mechanism theoretical capacities of up to 1000 mAh/g would be possible, thus, storing more energy than typical insertion materials. Interestingly, along with the commonality of the iron metal center, the materials often have spinel or inverse spinel structures. The densely packed structure of these spinel materials has led to the demonstration that smaller crystallite size samples can provide higher practical energy density than larger size samples. This presentation will provide insight into the role of crystallite size as well as the lithiation/delithiation mechanisms of this class of bimetallic iron oxide structures.