Operando XAFS and XRD Study of a Prussian Blue Analogue Cathode Material: Iron Hexacyanocobaltate

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.