The Importance of Surface Oxygen for Lithiation and Morphology Evolution during Calcination of High‐Nickel NMC Cathodes. Issue 16 (15th March 2022) - Wolfman, Mark
Abstract: Nanoscale morphology has a direct impact on the performance of materials for electrochemical energy storage. Despite this importance, little is known about the evolution of primary particle morphology nor its effect on chemical pathways during synthesis. In this study, operando characterization is combined with atomic‐scale and continuum simulations to clarify the relationship between morphology of cathode primary particles and their lithiation during calcination of LiNi0.8 Mn0.1 Co0.1 O2 (NMC‐811). This combined approach reveals a key role for surface oxygen adsorption in facilitating the lithiation reaction by promoting metal diffusion and oxidation, and simultaneously providing surface sites for lithium insertion. Furthermore, oxygen surface termination is shown to increase the activation energy for sintering, leading to smaller primary particle sizes at intermediate temperatures. Smaller particles provide both shorter diffusion lengths for lithium incorporation and increased surface site density for lithium insertion. These insights provide a foundation for more tailored syntheses of cathode materials with optimized performance characteristics. Abstract : Performance of Li‐ion battery cathodes is greatly influenced by calcination. In situ X‐ray diffraction and multi‐scale modeling are combined to show the role of surface oxygen in promoting lithium insertion into the intermediate rock salt phase, as well as controlling ripening of primary particles in this Ni‐rich layered cathode material.