Elucidating the Lithium Storage Mechanism of Ruthenium-doped Cerium Oxide Anodes via ex situ & operando X-ray Absorption Spectroscopy

Unravelling the lithium storage mechanism of alternative anode materials is critical for the ongoing development of lithium-ion batteries (LIBs). Previously, we have performed a comprehensive XAS characterization of various metal-doped CeO2 anode materials, in particular Fe-doped CeO2, revealing the atomic scale reduction of the dopant within the host structure. Our results provide information on the oxidation state of the cations upon cycling and on the structural mechanism of dopant incorporation and its effect on the de-/lithiation mechanism. We aim to extend the reaction mechanism to Ru-doped CeO2. Remarkably, doping CeO2 with 15 at-% Ru provides the highest capacity among all metal-doped CeO2 anodes studied so far. Ex situ & operando XANES spectra are pivotal for elaborating the evolution of valence states and the bonding state of the electroactive species. Longer ex situ EXAFS will reveal the evolution of coordination environment and local structure around Ru and Ce.