Significant Agglomeration of Conductive Materials and the Dispersion State Change of the Ni-Rich NMC-Based Cathode Slurry during Storage

The dispersion quality and the storage stability of the electrode slurry are very important industrial issues as they directly affect the productivity of the electrode process as well as the performance of the battery. To maintain the dispersion stability, the prepared electrode slurry is agitated in a storage tank before entering the subsequent coating process. However, our understanding on the dispersibility of electrode slurries during storage is not enough. In this study, we systematically investigate the changes in the dispersion state and the rheological properties of Ni-rich NMC-based cathode slurries under various agitating conditions during storage. Most of the conductive nanoparticles form large spherical agglomerates of several tens of micrometers under low-speed agitating conditions, resulting in a dramatic change in the rheological properties. We also report that the change in the dispersion state and the rheological properties during storage can be characterized by the hydrodynamic stress induced by the flow. The mechanism of change in the microstructure of the cathode slurry during storage can be understood by considering the relative affinity between the particles and the flow characteristics during agitation. This study clearly demonstrates how the cathode slurry should be cared during storage to prevent quality problems.