An investigation of the electrochemical delithiation process of carbon coated α-Fe2O3nanoparticles

Abstract

The electrochemical lithiation–delithiation of iron oxide is a rather complex process, which is still not fully understood. In this study we investigated the electrochemical lithiation–delithiation mechanism of hematite by means of X-ray diffraction (XRD), ⁵⁷Fe Mössbauer spectroscopy, high-resolution transmission electron microscopy (HRTEM) and X-ray absorption spectroscopy (XAS). Since the delithiation process has been so far less investigated, particular attention was dedicated to the characterization of the chemical species that are formed during this process. The results of this investigation indicated that at the end of the delithiation process lithium iron oxide α-LiFeO₂ is formed. The formation of this compound may be the explanation for the irreversible capacity loss in the first cycle, which is usually assigned to the formation of an organic gel-like layer. Based on these results a new charge–discharge mechanism of hematite in lithium-ion batteries (LIBs) is proposed and discussed.