Simultaneous in Situ X-ray Absorption Spectroscopy and X-ray Diffraction Studies on Battery Materials: The Case of Fe_0.5TiOPO₄

Following the reaction mechanisms of materials for Li-ion batteries under in situ conditions can provide vital new clues in the development of better battery materials. A new in situ cell was developed for such a purpose which allows an almost simultaneous measurement of XRD (X-ray diffraction) and XAS (X-ray absorption spectroscopy) at energies as low as the Ti K-edge. Change from one method to the other was possible in less than a minute at the Swiss–Norwegian Beamline (SNBL). Using this cell with its flexibility in terms of windows, it was proven that the reaction mechanism of iron titanium oxyphosphate (Fe 0.5 TiOPO 4 ) upon lithiation and delithiation consists of a combined insertion–conversion reaction with the mostly reversible reduction of Ti 4+ to Ti 2+ and Fe 2+ to Fe 0 .