Electrogenerated Hexacyanoferrate Thin Films for Battery Applications

Prussian Blue Analogues such as transition metal hexacyanoferrates (HCFs) have gained increasing interest as materials for energy storage applications, as they provide enhanced stability due to their open framework structure and potential for reduced cost by use of earth-abundant materials. Using Ni, NiCo and NiCu substrates, a variety of alloy HCF films were electrogenerated by cyclic in the presence of hexacyanoferrate. For NiCo- and NiCu-based HCF materials, the charge storage and transport properties were measured and compared to Ni-HCF to explore the effects of the addition of alloying metals. The addition of Co or Cu in the substrate results in a small increase in the total stored charge, but no observable trend in the transport kinetics. For Ni-HCF, the total amount of Fe in the resulting material was measured both electrochemically and with x-ray spectroscopic methods. Unexpectedly, the spectroscopic measurements were smaller than the electrochemical ones, indicating there must be additional electrochemical reactions occurring in the presence of the HCF.