The Missing Piece: The Structure of the Ti <sub>3</sub> C <sub>2</sub> T <sub> <i>x</i> </sub> MXene and Its Behavior as Negative Electrode in Sodium Ion Batteries
Chiara Ferrara, Antonio Gentile, Stefano Marchionna, Irene Quinzeni, Martina Fracchia, Paolo Ghigna, Simone Pollastri, C. Ritter, Giovanni Maria Vanacore, Riccardo Ruffο
Abstract
(T = F, O) shows outstanding stability as anode for sodium ion batteries (100% of capacity retention after 530 cycles with charge efficiency >99.7%). However, the reversibility of the intercalation/deintercalation process is strongly affected by the synthesis parameters determining, in turn, significant differences in the material structure. This study proposes a new approach to identify the crystal features influencing the performances, using a structural model built with a multitechnique approach that allows exploring the short-range order of the lamella. The model is then used to determine the long-range order by inserting defective elements into the structure. With this strategy it is possible to fit the MXene diffraction patterns, obtain the structural parameters including the stoichiometric composition of the terminations (neutron data), and quantify the structural disorder which can be used to discriminate the phases with the best electrochemical properties.