New Insights into the All-Dry Synthesis of NMC622 Cathodes Using a Single-Phase Rock Salt Oxide Precursor

In this study, new insights into the all-dry synthesis of the LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode using a single-phase rock-salt (RS) oxide precursor are provided. It was found that use of a larger amount of excess Li content not only can enhance the electrochemical performance of NMC made from the RS-precursor but also increase the degree of homogeneity of the NMC cathode material. In situ XRD analysis showed that lithiation of the RS-precursor (i.e., formation of the O3-phase) starts at a higher synthesis temperature (similar to 450 degrees C) than that is required when using a hydroxide precursor (HP) and lithium carbonate (similar to 350 degrees C). Consequently, Li2CO3 was consumed by the reaction with the HP at low temperatures before the temperature reached the Li2CO3 melting point. In contrast, the reduced lithiation kinetics of the RS-precursor results in the presence of liquid Li2CO3 during the synthesis, which rapidly increases the rates of precursor lithiation and increases the NMC primary particle size.