In Operando XANES & XRD Investigation into the Rate-Dependent Transport Properties of Lithium Iron Silicate Cathodes

The majority of improvements to LIB technology have come through the development of new novel cathode materials. One promising cathode material is Li 2 FeSiO 4 (LFS), desirable for its low cost and high theoretical capacity. However, the ionic conduction and transport mechanisms within this material are still not well understood, and require further investigation to improve upon cycling rate performance. To this end combined measurements of XRD & XANES have been performed in operando on LFS during electrochemical cycling, i.e. at selected electrochemical states of charge during the formation cycle the crystalline structure and the transition metal oxidation state as well as the site symmetry were characterized via the two aforementioned techniques. These in operando measurements expose once more a charging rate-dependent phase evolution during the formation cycle, which can be well characterized using a simplified equivalent circuit analogue.