Affiliation:
1. Department of Chemistry University of Illinois at Chicago Chicago IL 60607 USA
2. Chemical Sciences and Engineering Division Argonne National Laboratory Lemont IL 60439 USA
3. Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory Menlo Park CA 94025 USA
4. DND‐CAT Synchrotron Research Center Northwestern University Evanston IL 60208 USA
Abstract
AbstractLi‐rich disordered rocksalt (DRS) oxyfluorides have emerged as promising high‐energy cathode materials for lithium‐ion batteries. While a high level of fluorination in DRS materials offers performance advantages, it can only be achieved via mechanochemical synthesis, which poses challenges of reproducibility and scalability. The definition of relationships between fluorination and structural stability is required to devise alternative methods that overcome these challenges. In this study, the thermal evolution of three highly fluorinated phases, Li2TMO2F (TM = Mn, Co, and Ni), is investigated in an inert atmosphere. Diffraction and spectroscopic techniques are utilized to examine their electronic and chemical states up until conditions of decomposition. The analysis reveals that the materials phase‐separate above 400 °C, at most. It is also observed that heat‐treated DRS materials exhibit intricate changes in the local coordination of the metals, including their spin, and ordering compared to the pristine states. The changes upon annealing are accompanied by a modulation of the voltage profile, including reduced hysteresis, when used as electrodes. These results provide an in‐depth understanding of the fundamental crystal chemistry of DRS oxyfluorides in view of their promising role as the next generation of Li‐ion cathodes.
Funder
National Science Foundation
Basic Energy Sciences
Division of Materials Research
Subject
Electrochemistry,Condensed Matter Physics,Biomaterials,Electronic, Optical and Magnetic Materials