Physical property control for innovative powder processes – Rheological control of concentrated slurry and wet granules

Abstract

The manufacture of materials using slurry-based processes, such as the electrodes of Lithium ion secondary batteries and fuel cells, can be made more productive by increasing the concentration of the slurry or adopting wet granules with extremely high concentrations.Shear thickening, which is a particular issue for such highly concentrated slurries, is derived from collisions between particles, it is important to control the size, size distribution, and concentration of particles, as well as the solvent viscosity. Furthermore, the controlling of electrostatic interaction between particles and mixing of different size particles have direct impacts on shear thickening, the concentration of salt in the slurry and size and mixing ratio of particles are also important characteristics. It may be possible to control rheological behavior using these characteristics.The amount of solvent is reduced beyond the level in a concentrated slurry, the slurry changes from a so-called liquid state to a solid state of wet granules. Fully utilizing the properties of these wet granules would maximize various advantages in the production process. Flowability is the most important characteristic for use of highly concentrated wet granules. This research found that flowability is extremely low when the strain is low, but that higher wet granule concentrations flow more easily under high strain.Our latest research about rheological behavior of concentrated slurry and wet granules open up to the possibilities for ultimate form of the electrode manufacturing process might involve film-creation or forming using particles without any liquid content at all. Resolving issues such as the uniformity of the blended powder and flowability control may enable conventional slurry processes to be replaced by powder processes.