Abstract
The reversible electrochemical lithiation of potassium iron hexacyanocobaltate (FeCo) was studied by operando X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) assisted by chemometric techniques. In this way, it was possible to follow the system dynamics and retrieve structural and electronic transformations along cycling at both Fe and Co sites. These analyses confirmed that FeCo features iron as the main electroactive site. Even though the release of potassium ions causes a local disorder around the iron site, the material exhibits an excellent structural stability during the alkali ion deinsertion/insertion processes. An independent but interrelated analysis approach offers a good strategy for data treatment and provides a time-resolved picture of the studied system.
Highlights
The development of sustainable energy sources and the storage of electrical energy is a worldwide concern [1]
The call for an efficient electrochemical energy storage is answered by rechargeable batteries, which are based on high rate reaction of lithium ions into nano- and microstructured insertion materials [2,3,4,5,6]
The lattice parameter for the pristine electrode (a = 10,171 Å) differs from that derived from the powder, since the electrode was dehydrated before use, manifesting a negative thermal expansion effect [34]
Summary
The development of sustainable energy sources and the storage of electrical energy is a worldwide concern [1]. Prussian blue analogues (PBAs), and in particular, metal hexacyanoferrates, have gained considerable attention as insertion type materials due to the ease of preparation, effectiveness as electrode materials, and wide versatility towards several ions [7,8,9,10,11,12] The structure of such compound is characterized by a three-dimensional cubic network ( other crystal symmetries are found) of repeating –Fe–CN–M–NC– units, where iron and M sites are typically octahedrally coordinated. These structural features, together with the electroactivity of the constituting metals, form the basis for a vast range of applications, for instance, analyte sensors [13,14], magnetic devices [15], electrochromism [16], charge storage [17], supercapacitors [18,19], ion-exchange sieves [20,21], and even antibacterial agents against Escherichia coli and Staphylococcus aureus [22]
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