Influence of Transition-Metal Order on the Reaction Mechanism of LNMO Cathode Spinel: An <i>Operando</i> X-ray Absorption Spectroscopy Study
Marcus Fehse, Naiara Etxebarria, Laida Otaegui, Marta Cabello, Silvia Martín-Fuentes, Maria Angeles Cabañero, Icíar Monterrubio, Christian Fink Elkjær, Óscar Fabelo, Nahom Asres Enkubari, Juan Miguel López del Amo, Montse Casas‐Cabanas, Marine Reynaud
Abstract
An operando dual-edge X-ray absorption spectroscopy on both transition-metal ordered and disordered LiNi0.5Mn1.5O4 during electrochemical delithiation and lithiation was carried out. The large data set was analyzed via a chemometric approach to gain reliable insights into the redox activity and the local structural changes of Ni and Mn throughout the electrochemical charge and discharge reaction. Our findings confirm that redox activity relies predominantly on the Ni2+/4+ redox couple involving a transient Ni3+ phase. Interestingly, a reversible minority contribution of Mn3+/4+ is also evinced in both LNMO materials. While the reaction steps and involved reactants of both ordered and disordered LNMO materials generally coincide, we highlight differences in terms of reaction dynamics as well as in local structural evolution induced by the TM ordering.